Subject: Re: Seismograph for school From: ChrisAtUpw@....... Date: Sat, 30 Sep 2006 22:15:14 EDT In a message dated 2006/09/30, tchannel@.............. writes: > Hi Folks, I have a question about the coil and magnet portion of a sensor. > I have seen very small coils and magnets used and very large ones. I guess > the common one is about a 25# pull magnet and a coil of about 500 ohms? I am > going to rebuild my assembly for two reasons, first I have been told my cow > magnet and small coil is just too small. > The second reason is I just found a great cheap powerful magnet. It is the > size of a deck of cards, about 50# pull and about $8.00 at Harbor Freight. > > Using the same (everything) but three different magnet/coils, undersized, > just right, and oversized, what effects would they have, on the gain, final > image, etc? > > I would create a "pancake" coil about the same size as the magnet, square > in shape and thin. > > Your thought or suggestions please. If this is a good magnet to use in a > coil assembly or using two in a damper assembly, I can give you the part > number etc. They are welding assembly magnets, two in a package. Hi Ted, You don't need this size or bulk. You need quite a few thousand turns on a coil with the ID clear of the OD of the magnet, if you use a cow magnet. You do need a coil of 350 to 1000 Ohms to match your opamp input impedance. The greater the number of turns and the greater the change of flux (= area x field) through the coil, the greater the output. If you put an unshielded magnet on the arm of a seismometer, you are likely to detect every pulse on the house utility power wiring, fridges switching on and off, passing cars and trucks and changes in the Earth's field.... The signal is likely to be very noisy. The sensitivity of a seismic detection system needs to be very high. The usual coil / magnet system involves mounting the coil on the arm, sitting your magnet on the baseplate and using a non magnetic mass - brass is easy to use, but you can also use lead or copper. You need a linear high sensitivity response. You have to allow for tilt drift over the week of about 3/8" with a Lehman and the sensitivity needs to stay constant and linear within this range. This can be provided with a rectangular coil of maybe 2000 turns and a quad NdFeB magnet system on mild steel backing plates. I have described my detector system using four 1" square x 1/8" thick NdFeB magnets on 1/4" thick mild steel backing plates in the second half of http://jclahr.com/science/psn/chapman/lehman/index.html You may be able to extract the primary winding from a small low power mains transformer and use that? This is the sort which has side by side, not overlapping, P & S windings and a square / rectangular former. I don't know what is available to you? Larry sells round relay coils, but I prefer a larger rectangular form. You may also be able to buy 'spare' mains coils for timers and water flow valves on washing machines. Some have a suitable pancake form. The coil needs to have an internal rectangular measurement in the direction of motion of maybe 1/2" to 3/4" so that its output will be constant, allowing for the tilt drift on the seismometer. I also use an identical mild steel adjustable frame for the damping, but it uses a 1/16" copper plate and 1" x 1/2" x 1/4" thick NdFeB bar magnets. The damping tongue is mounted horizontally and the damping magnet block is simply slid further over it until you get ~0.7 critical damping. If you deflect the arm 10 mm and release it, it should swing 0.5 mm beyond the balance point before returning to balance. The damping force that you need decreases as the period set is increased, and increases with the seismic mass, so it needs to be easily adjustable. This construction is easy to set up and use and it is NOT temperature sensitive. This magnet + tongue damping arrangement is very effective. You can buy suitable NdFeB magnets from www.kjmagnetics.com. Regards, Chris Chapman In a me= ssage dated 2006/09/30, tchannel@.............. writes:

Hi Folks,  I have a questi= on about the coil and magnet portion of a sensor. I have seen very small coi= ls and magnets used and very large ones. I guess the common one is about a 2= 5# pull magnet and a coil of about 500 ohms? I am going to rebuild my assemb= ly for two reasons, first I have been told my cow magnet and small coil is j= ust too small. 
The second reason is I just found a great cheap powerful magnet.  It i= s the size of a deck of cards, about 50# pull and about $8.00 at Harbor Frei= ght.

Using the same (everything) but three different magnet/coils, undersized,=20= just right, and oversized, what effects would they have, on the gain, final=20= image, etc?

 I would create a "pancake" coil about the same size as the magnet, square=20= in shape and thin. 

Your thought or suggestions please.  If this is a good magnet to use=20= in a coil assembly or using two in a damper assembly, I can give you the par= t number etc.  They are welding assembly magnets, two in a package.


Hi Ted,

       You don't need this size or bulk.

       You need quite a few thousand turns on=20= a coil with the ID clear of the OD of the magnet, if you use a cow magnet. <= BR>
       You do need a coil of 350 to 1000 Ohms=20= to match your opamp input impedance.

       The greater the number of turns and the= greater the change of flux (=3D area x field) through the coil, the greater= the output.

       If you put an unshielded magnet on the=20= arm of a seismometer, you are likely to detect every pulse on the house util= ity power wiring, fridges switching on and off, passing cars and trucks and=20= changes in the Earth's field.... The signal is likely to be very noisy. The=20= sensitivity of a seismic detection system needs to be very high.

       The usual coil / magnet system involves= mounting the coil on the arm, sitting your magnet on the baseplate and usin= g a non magnetic mass - brass is easy to use, but you can also use lead or c= opper. You need a linear high sensitivity response. You have to allow for ti= lt drift over the week of about 3/8" with a Lehman and the sensitivity needs= to stay constant and linear within this range. This can be provided with a=20= rectangular coil of maybe 2000 turns and a quad NdFeB magnet system on mild=20= steel backing plates.

       I have described my detector system usi= ng four 1" square x 1/8" thick NdFeB magnets on 1/4" thick mild steel backin= g plates in the second half of  http://jclahr.com/science/psn/chapman/l= ehman/index.html

       You may be able to extract the primary=20= winding from a small low power mains transformer and use that? This is the s= ort which has side by side, not overlapping, P & S windings and a square= / rectangular former. I don't know what is available to you? Larry sells ro= und relay coils, but I prefer a larger rectangular form. You may also be abl= e to buy 'spare' mains coils for timers and water flow valves on washing mac= hines. Some have a suitable pancake form.

       The coil needs to have an internal rect= angular measurement in the direction of motion of maybe 1/2" to 3/4" so that= its output will be constant, allowing for the tilt drift on the seismometer= ..

       I also use an identical mild steel adju= stable frame for the damping, but it uses a 1/16" copper plate and 1" x 1/2"= x 1/4" thick NdFeB bar magnets. The damping tongue is mounted horizontally=20= and the damping magnet block is simply slid further over it until you get ~0= ..7 critical damping. If you deflect the arm 10 mm and release it, it should=20= swing 0.5 mm beyond the balance point before returning to balance. The dampi= ng force that you need decreases as the period set is increased, and increas= es with the seismic mass, so it needs to be easily adjustable. This construc= tion is easy to set up and use and it is NOT temperature sensitive. This mag= net + tongue damping arrangement is very effective.

       You can buy suitable NdFeB magnets from= www.kjmagnetics.com.

       Regards,

       Chris Chapman Subject: Re: Seismograph for school From: "Geoffrey" gmvoeth@........... Date: Sat, 30 Sep 2006 19:27:59 -0700 Hello Chris; Can you tell us how to get a uniform magnetic field to cut the coil at right angles (normal) to the windings ? can you use two opposing horse shoe magnets with a coil in the middle ? i should imagine a sturdy custom built non magnetic bracket is needed as well as great care not to let the magnets clap together or the impact might weaken the magnets. i think those horshoe magnets with a hole in the middle of the u is the way to go. regards; geoff __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismograph for school From: ChrisAtUpw@....... Date: Sat, 30 Sep 2006 23:58:52 EDT In a message dated 2006/10/01, gmvoeth@........... writes: > Hello Chris; > Can you tell us how to get a uniform magnetic field > to cut the coil at right angles (normal) to the windings ? Hi Geoff, I use 4 off 1" sq x 1/8" rectangular NdFeB magnets on two 3.5" x 2" x 1/4" thick mild steel backing plates and mount the coil in between. You have N+S magnets on one face opposite to S+N magnets on the other face. This gives a high central field and a linear movement response. I use a rectangular pancake coil of about 2000 turns. It is quite effective! See http://jclahr.com/science/psn/chapman/lehman/index.html > can you use two opposing horse shoe magnets > with a coil in the middle ? This is likely to give a lower sensitivity and is more difficult to make / mount. Large Alnico U magnets are quite expensive. You benefit from the relatively high flux of the NdFeB magnets. Regards, Chris Chapman In a me= ssage dated 2006/10/01, gmvoeth@........... writes:

Hello Chris;
Can you tell us how to get a uniform magnetic field
to cut the coil at right angles (normal) to the windings ?


Hi Geoff,

       I use 4 off 1" sq x 1/8" rectangular Nd= FeB magnets on two 3.5" x 2" x 1/4" thick mild steel backing plates and moun= t the coil in between. You have N+S magnets on one face opposite to S+N magn= ets on the other face. This gives a high central field and a linear movement= response. I use a rectangular pancake coil of about 2000 turns. It is quite= effective!

       See  http://jclahr.com/science/psn= /chapman/lehman/index.html

can you use two opposing horse=20= shoe magnets
with a coil in the middle ?


       This is likely to give a lower sensitiv= ity and is more difficult to make / mount. Large Alnico U magnets are quite=20= expensive. You benefit from the relatively high flux of the NdFeB magnets.
       Regards,

       Chris Chapman Subject: Re: Seismograph for school From: "Geoffrey" gmvoeth@........... Date: Sun, 1 Oct 2006 00:40:52 -0700 Hello Chris; http://jclahr.com/science/psn/chapman/lehman/index.html Yes, I like that design very much. Do you make a vertical version of that with a spring where the wire is ? I would like very much to either buy a kit or the plans from you to build my own vertical. I lack talent in your area I need help to make a decent sensor. Vertical is my only interest unless I can get a planer type sensor in the horizontal. Meaning a single sensor for both EW/NS. Please email me the details. gmvoeth@........... gmvoeth@......... gmvoeth@......... any one of those three addresses. I have seen a novel sensor at ASU about 1985 where two masses are N/S and E/W but vertically at a 45 degree angle or so making it possible to reproduce three dimensional motion with only two sensors. Or so it seemed to me. I have never seen that design on the Internet. regards; geoff __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismograph for school From: ChrisAtUpw@....... Date: Sun, 1 Oct 2006 15:39:26 EDT In a message dated 2006/10/01, gmvoeth@........... writes: > Hello Chris; > http://jclahr.com/science/psn/chapman/lehman/index.html > Yes, I like that design very much. > > Do you make a vertical version of that > with a spring where the wire is ? Hi Geoff, Not at the moment. Long period verticals are much more difficult to make than long period horizontals. The essential properties to give a 'zero length extension spring' were worked out by LaCoste in the mid 1930's. See http://psn.quake.net/bibliography.html To balance the vertical force of gravity on the mass requires a very constant force. You need a Ni-SpanC spring and a lot of careful design to enable you to get stable periods over about 10 secs. The elastic properties of steel springs are much too temperature sensitive. One alternative is to use a steel leaf spring, but to provide electronic force feedback to both compensate for incoming signals and to remove the drift. The feedback essentially tries to hold the mass stationary. See great example at http://www.bryantlabs.net/seismo.html Another alternative is to use a steel spring to produce a vertical with a period of 1 to 3 seconds, which is not too difficult to do and then extend the response electronically by x10 to x20 - as you can for a geophone (Roberts' circuit). You could probably extend the period of your 1 Hz geophone to about ~20 sec this way, but you would likely see some increase in sensor noise. This period extension method is attempted on the AS-1. See http://jclahr.com/science/psn/as1/index.html The basic period is about 1.5 sec and a response from 3Hz to 20 sec is claimed, but the manufactured item costs about US $600. Regards, Chris Chapman In a me= ssage dated 2006/10/01, gmvoeth@........... writes:

Hello Chris;
http://jclahr.com/science/psn/chapman/lehman/index.html
Yes, I like that design very much.

Do you make a vertical version of that
with a spring where the wire is ?


Hi Geoff,

       Not at the moment.

       Long period verticals are much more dif= ficult to make than long period horizontals. The essential properties to giv= e a 'zero length extension spring' were worked out by LaCoste in the mid 193= 0's. See http://psn.quake.net/bibliography.html To balance the vertical forc= e of gravity on the mass requires a very constant force. You need a Ni-SpanC= spring and a lot of careful design to enable you to get stable periods over= about 10 secs. The elastic properties of steel springs are much too tempera= ture sensitive.

       One alternative is to use a steel leaf=20= spring, but to provide electronic force feedback to both compensate for inco= ming signals and to remove the drift. The feedback essentially tries to hold= the mass stationary. See great example at http://www.bryantlabs.net/seismo.= html

       Another alternative is to use a steel s= pring to produce a vertical with a period of 1 to 3 seconds, which is not to= o difficult to do and then extend the response electronically by x10 to x20=20= - as you can for a geophone (Roberts' circuit). You could probably extend th= e period of your 1 Hz geophone to about ~20 sec this way, but you would like= ly see some increase in sensor noise.

       This period extension method is attempt= ed on the AS-1. See http://jclahr.com/science/psn/as1/index.html The basic p= eriod is about 1.5 sec and a response from 3Hz to 20 sec is claimed, but the= manufactured item costs about US $600.

       Regards,

       Chris Chapman Subject: Re: Seismograph for school From: "meredith lamb" paleoartifact@......... Date: Sun, 1 Oct 2006 14:04:12 -0600 Hi all, There is a choice of magnet distributors one can entertain for purchasing magnets of course. "Magnets4less" Lists magnets roughly for alot less (~1/3 to 1/4) the price of KJMagnetics. The problem with Magnet4less is they have a minimum order of ~$30.00.....and....their shipping/handling charge of ~$8 or so, is afew dollars more, and its the ultra slow UPS, and their personnel at that place. KJMagnetics ships fast, and usually a flat rate via USPS. KJMagnetics also has a minimum quantity order (~usually 10 of whatever size), as does Magnets4less which can get up to 20 minimum ....for the sizes entertained here. Its worth comparison shopping I suppose .....for example: KJMagnetics: 1x1x1/8"= qty of 10 @ 29.15 ($2.91 each) Magnets4less: 1x1x1/8"= qty of 20 @..... ($0.98 each) Well made horizontal Chris! Still trying to quess what the boom pivot actually is.....perhaps a single wire vertical between the blocks and the boom end center pivots on such?? (can't see on the photo) Take care, Meredith Lamb On 9/30/06, ChrisAtUpw@....... wrote: > > In a message dated 2006/10/01, gmvoeth@........... writes: > > Hello Chris; > Can you tell us how to get a uniform magnetic field > to cut the coil at right angles (normal) to the windings ? > > > > Hi Geoff, > > I use 4 off 1" sq x 1/8" rectangular NdFeB magnets on two 3.5" x 2" > x 1/4" thick mild steel backing plates and mount the coil in between. You > have N+S magnets on one face opposite to S+N magnets on the other face. This > gives a high central field and a linear movement response. I use a > rectangular pancake coil of about 2000 turns. It is quite effective! > > See http://jclahr.com/science/psn/chapman/lehman/index.html > > can you use two opposing horse shoe magnets > with a coil in the middle ? > > > > This is likely to give a lower sensitivity and is more difficult to > make / mount. Large Alnico U magnets are quite expensive. You benefit from > the relatively high flux of the NdFeB magnets. > > Regards, > > Chris Chapman Hi all,

There is a choice of magnet distributors one can entertain for purchasing
magnets of course.  "Magnets4less" Lists magnets roughly for alot less
(~1/3 to 1/4) the price of KJMagnetics.  The problem with Magnet4less
is they have a minimum order of ~$30.00.....and....their shipping/handling
charge of ~$8 or so, is afew dollars more, and its the ultra slow UPS, and
their personnel at that place.  KJMagnetics ships fast, and usually a flat rate
via USPS.  KJMagnetics also has a minimum quantity order (~usually 10
of whatever size), as does Magnets4less which can get up to 20 minimum
....for the sizes entertained here.  Its worth comparison shopping I suppose
.....for example:

KJMagnetics:    1x1x1/8"= qty of 10 @ 29.15 ($2.91 each)
Magnets4less:   1x1x1/8"= qty of 20 @..... ($0.98 each)

Well made horizontal Chris!  Still trying to quess what the boom
pivot actually is.....perhaps a single wire vertical between the blocks and
the boom end center pivots on such?? (can't see on the photo)

Take care, Meredith Lamb

 
On 9/30/06, ChrisAtUpw@....... <ChrisAtUpw@.......> wrote:
In a message dated 2006/10/01, gmvoeth@........... writes:

Hello Chris;
Can you tell us how to get a uniform magnetic field
to cut the coil at right angles (normal) to the windings ?


Hi Geoff,

       I use 4 off 1" sq x 1/8" rectangular NdFeB magnets on two 3.5" x 2" x 1/4" thick mild steel backing plates and mount the coil in between. You have N+S magnets on one face opposite to S+N magnets on the other face. This gives a high central field and a linear movement response. I use a rectangular pancake coil of about 2000 turns. It is quite effective!

       See  http://jclahr.com/science/psn/chapman/lehman/index.html

can you use two opposing horse shoe magnets
with a coil in the middle ?


        This is likely to give a lower sensitivity and is more difficult to make / mount. Large Alnico U magnets are quite expensive. You benefit from the relatively high flux of the NdFeB magnets.

       Regards,

       Chris Chapman

Subject: Re: Seismograph for school From: Bobhelenmcclure@....... Date: Sun, 1 Oct 2006 21:21:16 EDT Hi all, I agree with Chris Chapman on the design of magnets and coils for horizontal sensors. Those who have an interest in building their own sensors should take a look at mine on John Lahr's web site, especially page _http://www.jclahr.com/science/psn/mcclure/horiz2.html_ (http://www.jclahr.com/science/psn/mcclure/horiz2.html) I operate three sensors for Z, N, and E. They are adjusted to fairly short natural periods, ranging from 5 to 14 seconds. I extend their effective period to 24 seconds by a digital filter of my own design, with excellent results. The magnets I recommend are available for $5.50 each, 50mm x 18mm x 6mm block magnet, from _http://www.gaussboys.com_ (http://www.gaussboys.com) You will need four of them and two pieces of 1/4 inch flat steel, two inches by three inches, and four steel bolts to make a magnet assembly. You do not necessarily need separate damping magnets. Just shunt the pickup coil with the appropriate resistance. Bob McClure Locust Valley, NY
Hi all,
 
  I agree with Chris Chapman on the design of magnets and coils fo= r=20 horizontal sensors. Those who have an interest in building their own sensors= =20 should take a look at mine on John Lahr's web site, especially page http://www.jc= lahr.com/science/psn/mcclure/horiz2.html
 
  I operate three sensors for Z, N, and E. They are adjusted to fa= irly=20 short natural periods, ranging from 5 to 14 seconds. I extend their effectiv= e=20 period to 24 seconds by a digital filter of my own design, with excellent=20 results.
 
  The magnets I recommend are available for $5.50 each, 50mm x 18m= m x=20 6mm block magnet, from http://www.gaussboys.com  You wil= l need=20 four of them and two pieces of 1/4 inch flat steel, two inches by three inch= es,=20 and four steel bolts to make a magnet assembly. You do not necessarily need=20 separate damping magnets. Just shunt the pickup coil with the appropriate=20 resistance.
 
Bob McClure
Locust Valley, NY
 Subject: Re: Seismograph for school From: ChrisAtUpw@....... Date: Sun, 1 Oct 2006 22:58:49 EDT In a message dated 2006/10/02, Bobhelenmcclure@....... writes: > I agree with Chris Chapman on the design of magnets and coils for > horizontal sensors. Hi Bob, Thanks! Chris In a me= ssage dated 2006/10/02, Bobhelenmcclure@....... writes:

I agree with Chris Chapman on=20= the design of magnets and coils for horizontal sensors.


Hi Bob,

       Thanks!

       Chris Subject: Re: Seismograph for school From: "tchannel" tchannel@.............. Date: Sun, 1 Oct 2006 22:12:06 -0600 Hi Bob, Thanks for the great picture. I really liked your ideas and = also the great one that Chris made. Chris posted a drawing showing the magnet layout. Two magnets on top, = end to end N to S, I think, and on the bottom two magnets end to end S = to N. I find they make these magnets with the N and S poles in various = arrangement. I don't remember the terms but are your poles on the ends or on the Axially (through 6mm = thickness)? In other words, laying flat, face up, North and flip it = over and that side is South? I made my first sensor, using a cow magnet and a coil in the shape of a = spool, the cow magnet's, North pole, only fits into the spool hole, to = the center point. If the pendulum move right, the North pole moves from = center to the end of the spool, if it move left the North pole moves = from the center of the spool to the entrance of the spool. It does = work, but I see these are much better arrangement. After reading these postings, I have a much better ideas about the coil = size and proper wire size. On the other hand I see picture of huge huge = magnets and coil. Is there a measurement in mv's or other test to tell = if one has made a coil/magnet arrangement which is proper in output? Thanks, for the ideas, Ted ----- Original Message -----=20 From: Bobhelenmcclure@.......... To: psn-l@................. Sent: Sunday, October 01, 2006 7:21 PM Subject: Re: Seismograph for school Hi all, I agree with Chris Chapman on the design of magnets and coils for = horizontal sensors. Those who have an interest in building their own = sensors should take a look at mine on John Lahr's web site, especially = page http://www.jclahr.com/science/psn/mcclure/horiz2.html I operate three sensors for Z, N, and E. They are adjusted to fairly = short natural periods, ranging from 5 to 14 seconds. I extend their = effective period to 24 seconds by a digital filter of my own design, = with excellent results. The magnets I recommend are available for $5.50 each, 50mm x 18mm x = 6mm block magnet, from http://www.gaussboys.com You will need four of = them and two pieces of 1/4 inch flat steel, two inches by three inches, = and four steel bolts to make a magnet assembly. You do not necessarily = need separate damping magnets. Just shunt the pickup coil with the = appropriate resistance. Bob McClure Locust Valley, NY
Hi Bob,  Thanks for the great picture.  I really liked = your ideas=20 and also the great one that Chris made.
Chris posted a drawing showing the magnet layout.  Two magnets = on top,=20 end to end N to S, I think, and on the bottom two magnets end to end S = to=20 N.   I find they make these magnets with the N and S poles in = various=20 arrangement.  I don't remember the terms
but are your poles on the ends or on the Axially (through 6mm=20 thickness)?   In other words, laying flat, face up, North and = flip it=20 over and that side is South?
 
I made my first sensor, using a cow magnet and a coil in the shape = of a=20 spool,  the cow magnet's, North pole, only fits into the spool = hole, to the=20 center point.  If the pendulum move right, the North pole = moves from=20 center to the end of the spool, if it move left the North pole moves = from the=20 center of the spool to the entrance of the spool.   It does = work, but=20 I see these are much better arrangement.
 
After reading these postings, I have a much better ideas about the = coil=20 size and proper wire size.  On the other hand I see picture of huge = huge=20 magnets and coil.   Is there a measurement in mv's or other = test to=20 tell if one has made a coil/magnet arrangement which is proper in = output?
 
Thanks, for the ideas,  Ted
----- Original Message -----
From:=20 Bobhelenmcclure@....... =
Sent: Sunday, October 01, 2006 = 7:21=20 PM
Subject: Re: Seismograph for = school

Hi all,
 
  I agree with Chris Chapman on the design of magnets and = coils for=20 horizontal sensors. Those who have an interest in building their own = sensors=20 should take a look at mine on John Lahr's web site, especially page http://www= ..jclahr.com/science/psn/mcclure/horiz2.html
 
  I operate three sensors for Z, N, and E. They are adjusted = to=20 fairly short natural periods, ranging from 5 to 14 seconds. I extend = their=20 effective period to 24 seconds by a digital filter of my own design, = with=20 excellent results.
 
  The magnets I recommend are available for $5.50 each, 50mm = x 18mm=20 x 6mm block magnet, from http://www.gaussboys.com  = You will=20 need four of them and two pieces of 1/4 inch flat steel, two inches by = three=20 inches, and four steel bolts to make a magnet assembly. You do not = necessarily=20 need separate damping magnets. Just shunt the pickup coil with the = appropriate=20 resistance.
 
Bob McClure
Locust Valley, NY
Subject: Magnests and coil for PVC seismometer & more From: jonfr500@......... Date: Mon, 2 Oct 2006 05:45:38 +0000 Hi all My Gentoo Linux hard drive is dieing on me (it's not dead, it's giving erro= rs), so I have to use webmail until I can replace it and get my system back= up. I am going to start to build my PVC seismometer this month, what I am hopef= ully going to buy this month are three things. Pair of magnets (no larger t= hen 4 cm in diamater), a coil and a resistance (like they use in geophones)= .. I need a suggestions on the magets, the coil and the resistance. The natr= ual frequancy of the PVC seismometer is ment to be 1Hz, that is a good plac= e for me to start. Regards. J=F3n Fr=EDmann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Sensor calibration From: Bobhelenmcclure@....... Date: Mon, 2 Oct 2006 22:00:43 EDT I have been asked about sensor calibration. For my thoughts, please go to _http://www.seismicnet.com/psnlist/index04.html_ (http://www.seismicnet.com/psnlist/index04.html) to see my letter on the subject, submitted on Tue. 13 Jul 2004 19:33:44 GMT. I have used both the methods described there for my own sensors. Cheers, Bob McClure
  I have been asked about sensor calibration. For my thoughts, ple= ase=20 go to
http://www.seismicne= t.com/psnlist/index04.html to=20 see my letter on the subject, submitted on Tue. 13 Jul 2004 19:33:44 GMT. I=20= have=20 used both the methods described there for my own sensors.
 
Cheers,
 
Bob McClure
 Subject: Re: Seismograph for school From: "tchannel" tchannel@.............. Date: Tue, 3 Oct 2006 10:28:57 -0600 Hi Bob, I have questions about your great Horz. sensor and the picture. 1. You used solder for the mass, is the mass volume fixed or is there a = wide range of weights, one could use. I guess the mass is to overcome = the friction of the hinge and stay stationary. The reason I ask is I = see a wide range of masses, but most around 5#. What is yours? and what = is your beam length? 2. Again the solder, is non magnetic is this important as I see many = things use as mass including iron? 3. I see you used a resistor as a damp, and not a external damper = device. I have read about doing this, but could not understand the = values for the resistor. You used 94k (in parallal?) acrossed the coil? = How did you arrive at that value? 4. You indicate to use a 100k in place of the 10k when using Larry's = amp, which I will be using. Why is that? 5. The placement of the sensor: Could it be on other than a concrete = floor, a normal wood floor? Could it be on carpet? I know that is not = the best choice, but many schools have such floors. Or should one not = bother with any other surface but a concrete floor? Thanks for your advise, and "well done!" Ted ----- Original Message -----=20 From: Bobhelenmcclure@.......... To: psn-l@................. Sent: Sunday, October 01, 2006 7:21 PM Subject: Re: Seismograph for school Hi all, I agree with Chris Chapman on the design of magnets and coils for = horizontal sensors. Those who have an interest in building their own = sensors should take a look at mine on John Lahr's web site, especially = page http://www.jclahr.com/science/psn/mcclure/horiz2.html I operate three sensors for Z, N, and E. They are adjusted to fairly = short natural periods, ranging from 5 to 14 seconds. I extend their = effective period to 24 seconds by a digital filter of my own design, = with excellent results. The magnets I recommend are available for $5.50 each, 50mm x 18mm x = 6mm block magnet, from http://www.gaussboys.com You will need four of = them and two pieces of 1/4 inch flat steel, two inches by three inches, = and four steel bolts to make a magnet assembly. You do not necessarily = need separate damping magnets. Just shunt the pickup coil with the = appropriate resistance. Bob McClure Locust Valley, NY
Hi Bob,  I have questions about your great Horz. sensor and = the=20 picture.
 
1. You used solder for the mass,  is the mass volume fixed or = is there=20 a wide range of weights, one could use.  I guess the mass is to = overcome=20 the friction of the hinge and stay stationary.  The reason I ask is = I see a=20 wide range of masses, but most around 5#.  What is yours? and what = is your=20 beam length?
 
2. Again the solder, is non magnetic is this important as I see = many things=20 use as mass including iron?
 
3.  I see you used a resistor as a damp, and not a external = damper=20 device.  I have read about doing this, but could not understand the = values=20 for the resistor.  You used 94k (in parallal?) acrossed the = coil?  How=20 did you arrive at that value?
 
4. You indicate to use a 100k in place of the 10k when using = Larry's=20 amp,  which I will be using.  Why is that?
 
5.  The placement of the sensor:  Could it be on other = than a=20 concrete floor, a normal wood floor?  Could it be on carpet?  = I know=20 that is not the best choice, but many schools have such floors.  Or = should=20 one not bother with any other surface but a concrete floor?
 
Thanks for your advise, and "well done!"   Ted
----- Original Message -----
From:=20 Bobhelenmcclure@....... =
Sent: Sunday, October 01, 2006 = 7:21=20 PM
Subject: Re: Seismograph for = school

Hi all,
 
  I agree with Chris Chapman on the design of magnets and = coils for=20 horizontal sensors. Those who have an interest in building their own = sensors=20 should take a look at mine on John Lahr's web site, especially page http://www= ..jclahr.com/science/psn/mcclure/horiz2.html
 
  I operate three sensors for Z, N, and E. They are adjusted = to=20 fairly short natural periods, ranging from 5 to 14 seconds. I extend = their=20 effective period to 24 seconds by a digital filter of my own design, = with=20 excellent results.
 
  The magnets I recommend are available for $5.50 each, 50mm = x 18mm=20 x 6mm block magnet, from http://www.gaussboys.com  = You will=20 need four of them and two pieces of 1/4 inch flat steel, two inches by = three=20 inches, and four steel bolts to make a magnet assembly. You do not = necessarily=20 need separate damping magnets. Just shunt the pickup coil with the = appropriate=20 resistance.
 
Bob McClure
Locust Valley, NY
Subject: Locating earthqukes with winquake From: jonfr500@......... Date: Tue, 3 Oct 2006 18:20:26 +0000 Hi Is it possible for me to locate earthquakes with Winquake ? Becose I am goi= ng to setup a remote station soon, problay after 2 - 3 months (depending on= few things). The remote station won't be internet connected, but I will co= llect data from it once a month. Sometimes next week I will also get one sensor reading regarding a earthqua= ke that I did detect this summer, I am going to attemt to locate that earth= quake to some exstent just by using two stations. Regards. J=F3n Fr=EDmann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Locating earthqukes with winquake From: ChrisAtUpw@....... Date: Tue, 3 Oct 2006 18:53:16 EDT In a message dated 2006/10/03, jonfr500@......... writes: > Is it possible for me to locate earthquakes with Winquake ? Because I am > going to setup a remote station soon, probably after 2 - 3 months (depending on > few things). The remote station won't be internet connected, but I will > collect data from it once a month. > > Sometimes next week I will also get one sensor reading regarding an > earthquake that I did detect this summer, I am going to attempt to locate that > earthquake to some existent just by using two stations. Hi Jon, Before you spend any money.... The P wave may travel at ~8 km /sec. You are going to need fairly widely separated stations to get a reasonably accurate angle estimate, depending on the distance. You can determine the approximate distance from the P-S interval. Can you get on-line signals from one of the Icelandic seismic stations as your second source? At least to try out? If you are going to use this method, you will need precision timing at all times, about 0.1 sec or better. You are lucky if the software clock on a computer is accurate to 30 sec / day! They are hopeless for seismic work. This is likely to need a GPS receiver at both stations. Could you use an internet link? What sort of sensors were you planning to use? Regional and teleseismic quakes need a response down to 0.5 Hz. Regards, Chris Chapman In a me= ssage dated 2006/10/03, jonfr500@......... writes:

Is it possible for me to locate= earthquakes with Winquake ? Because I am going to setup a remote station so= on, probably after 2 - 3 months (depending on few things). The remote statio= n won't be internet connected, but I will collect data from it once a month.=

Sometimes next week I will also get one sensor reading regarding an earthqua= ke that I did detect this summer, I am going to attempt to locate that earth= quake to some existent just by using two stations.


Hi Jon,

       Before you spend any money....

       The P wave may travel at ~8 km /sec. Yo= u are going to need fairly widely separated stations to get a reasonably acc= urate angle estimate, depending on the distance. You can determine the appro= ximate distance from the P-S interval. Can you get on-line signals from one=20= of the Icelandic seismic stations as your second source? At least to try out= ?

       If you are going to use this method, yo= u will need precision timing at all times, about 0.1 sec or better. You are=20= lucky if the software clock on a computer is accurate to 30 sec / day! They=20= are hopeless for seismic work. This is likely to need a GPS receiver at both= stations.

       Could you use an internet link?

       What sort of sensors were you planning=20= to use? Regional and teleseismic quakes need a response down to 0.5 Hz.

       Regards,

       Chris Chapman Subject: Re: Locating earthqukes with winquake From: jonfr500@......... Date: Tue, 3 Oct 2006 23:23:37 +0000 Hi The distanst between the stations is going to be ~11 km. I am going to use = gps clock on both stations, it is a standard that I have implimented at cur= rent date. All IMO stations are digital stations and I cannot lisen to them. They also= use there own specalised decoding software, that I don't have accsess to. = But I can request a data from IMO and then I get a sac binary format files,= that I convert to psn format. The second station is going to use 4.5Hz geophone, like the one I have. The= second station is going to sit directly on a bedrock, no sand, nothing of = such short. I cannot have a internet connection, becose this is out in the = country side and the location doesn't have a fone line. Even then the only = connection option is a ISDN at 9.6kbps as speed, if I don't want to pay pr = min, charge. Regards. J=F3n Fr=EDmann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismograph for school From: ChrisAtUpw@....... Date: Tue, 3 Oct 2006 21:00:29 EDT In a message dated 2006/10/03, tchannel@.............. writes: > 1. You used solder for the mass, is the mass volume fixed or is there a > wide range of weights, one could use. I guess the mass is to overcome the > friction of the hinge and stay stationary. The reason I ask is I see a wide range > of masses, but most around 5#. What is yours? and what is your beam length? Hi Ted, The period of a simple pendulum T = 2 x Pi x sqrt(L / g) where L is t he length in m and g = 9.81 m / sec^2. With a garden gate arrangement you can extend the period by x20 or more, but this gets increasingly difficult since the suspension angles get tiny and you may get dimensional / temperature associated lack of stability. Make the cross bar width ~1/3 the base length. There are pendulum design sheets on John Lahr's website. If A is the angle between the vertical and the rotation axis of the gate, you multiply g in the equation above by sine A. You will be using tilts of less than 1 degree. A 22" arm (1.5 ec) set to 20 sec requires an angle of 0.322 deg; set to 30 sec it requires 0.143 deg. The period is independent of the mass of the pendulum, but depends on the 'radius of gyration' of the whole moving system. A heavy connecting beam can significantly reduce this. A reasonable mass is 1 to 2 lbs with about a 2 ft arm - 1.5 sec. If you use more weight than this, you will need a strong top suspension. I suggest that you work out this force and look up the strength of your wire? The idea behind the suspension is that there should be as little friction as possible. Pre electronic seismometers used mechanical lever gain linkages to move the pen and hence needed a large mass to overcome the friction. > 2. Again the solder, is non magnetic is this important as I see many things > use as mass including iron? I don't use any magnetic materials on the boom 'in principle'. You won't know for sure what is a magnetic interaction and what is seismic. If I am taking the time and effort to build a seismometer, avoiding obvious problems just makes good sense. Like put the pickup coil on the arm and the magnets on the baseplate! > 3. I see you used a resistor as a damp, and not a external damper device. > I have read about doing this, but could not understand the values for the > resistor. You used 94k (in parallel?) acrossed the coil? How did you arrive > at that value? Experiment. Exactly the same principle - any relative movement induces a voltage in the coil proportionate to the magnetic field, the number of turns on the coil, the velocity and the circuit resistance provides the damping loss. The lower this resistance, the greater the loss, but this also reduces the output voltage. Not significantly in this design, since the magnetic field and coupling are very high and the mass is low. > 4. You indicate to use a 100k in place of the 10k when using Larry's amp, > which I will be using. Why is that? Because an input resistor of 10 K is less than the required damping resistor for this particular sensor design. > 5. The placement of the sensor: Could it be on other than a concrete > floor, a normal wood floor? Could it be on carpet? I know that is not the best > choice, but many schools have such floors. Or should one not bother with any > other surface but a concrete floor? You are likely to find wood floors both noisy and lacking tilt stability - can be critical for a long period Lehman. I can't say no, but try it with little expectation of success? You can put wide melamine shelving on a carpet and add weight to hold it firm, but the thicker the carpet the lower the stability. Expect drift with temperature, humidity and time. Bricks? On a concrete floor, I stick on 2" squares of 1/8" SS plate with pool adhesive to provide a good base for the adjusting screws. Regards, Chris Chapman In a me= ssage dated 2006/10/03, tchannel@.............. writes:

1. You used solder for the mass= ,  is the mass volume fixed or is there a wide range of weights, one co= uld use. I guess the mass is to overcome the friction of the hinge and stay=20= stationary. The reason I ask is I see a wide range of masses, but most aroun= d 5#.  What is yours? and what is your beam length?


Hi Ted,

       The period of a simple pendulum T =3D 2= x Pi x sqrt(L / g) where L is the length in m and g =3D 9.81 m / sec^2. Wit= h a garden gate arrangement you can extend the period by x20 or more, but th= is gets increasingly difficult since the suspension angles get tiny and you=20= may get dimensional / temperature associated lack of stability. Make the cro= ss bar width ~1/3 the base length. There are pendulum design sheets on John=20= Lahr's website. If A is the angle between the vertical and the rotation axis= of the gate, you multiply g in the equation above by sine A.  You will= be using tilts of less than 1 degree. A 22" arm (1.5 ec) set to 20 sec requ= ires an angle of 0.322 deg; set to 30 sec it requires 0.143 deg.
       The period is independent of the mass o= f the pendulum, but depends on the 'radius of gyration' of the whole moving=20= system. A heavy connecting beam can significantly reduce this. A reasonable=20= mass is 1 to 2 lbs with about a 2 ft arm - 1.5 sec. If you use more weight t= han this, you will need a strong top suspension. I suggest that you work out= this force and look up the strength of your wire?
       The idea behind the suspension is that=20= there should be as little friction as possible. Pre electronic seismometers=20= used mechanical lever gain linkages to move the pen and hence needed a large= mass to overcome the friction.

2. Again the solder, is non mag= netic is this important as I see many things use as mass including iron?

       I don't use any magnetic materials on=20= the boom 'in principle'. You won't know for sure what is a magnetic interact= ion and what is seismic. If I am taking the time and effort to build a seism= ometer, avoiding obvious problems just makes good sense. Like put the pickup= coil on the arm and the magnets on the baseplate!

3.  I see you used a resis= tor as a damp, and not a external damper device.  I have read about doi= ng this, but could not understand the values for the resistor.  You use= d 94k (in parallel?) acrossed the coil?  How did you arrive at that val= ue?


       Experiment. Exactly the same principle= - any relative movement induces a voltage in the coil proportionate to the=20= magnetic field, the number of turns on the coil, the velocity and the circui= t resistance provides the damping loss. The lower this resistance, the great= er the loss, but this also reduces the output voltage. Not significantly in=20= this design, since the magnetic field and coupling are very high and the mas= s is low.

4. You indicate to use a 100k i= n place of the 10k when using Larry's amp, which I will be using. Why is tha= t?


       Because an input resistor of 10 K is l= ess than the required damping resistor for this particular sensor design.
5.  The placement of the=20= sensor: Could it be on other than a concrete floor, a normal wood floor? Cou= ld it be on carpet? I know that is not the best choice, but many schools hav= e such floors. Or should one not bother with any other surface but a concret= e floor?


       You are likely to find wood floors both= noisy and lacking tilt stability - can be critical for a long period Lehman= ..  I can't say no, but try it with little expectation of success? You c= an put wide melamine shelving on a carpet and add weight to hold it firm, bu= t the thicker the carpet the lower the stability. Expect drift with temperat= ure, humidity and time. Bricks? On a concrete floor, I stick on 2" squares o= f 1/8" SS plate with pool adhesive to provide a good base for the adjusting=20= screws.

       Regards,

       Chris Chapman Subject: Re: Locating earthqukes with winquake From: "Thomas Dick" dickthomas01@............. Date: Tue, 3 Oct 2006 20:20:07 -0500 what about using radio to connect to you computer like they are doing in Washington State, USA? __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Locating earthqukes with winquake From: jonfr500@......... Date: Wed, 4 Oct 2006 01:51:45 +0000 Hi There is a big mountin in between. I can't brodcast over it. I also think t= hat I might need a premission for such type of radio transmission, it probl= ay costs money. Regards. J=F3n Fr=EDmann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismograph for school From: Ben Bradley benbradley@............... Date: Tue, 03 Oct 2006 21:59:10 -0400 ChrisAtUpw@....... wrote: > In a message dated 2006/10/03, tchannel@.............. writes: >>2. Again the solder, is non magnetic is this important as I see many things >>use as mass including iron? > > > I don't use any magnetic materials on the boom 'in principle'. You > won't know for sure what is a magnetic interaction and what is seismic. If I am > taking the time and effort to build a seismometer, avoiding obvious problems > just makes good sense. Like put the pickup coil on the arm and the magnets on > the baseplate! This makes good sense for eliminating magnetic effects on the boom, but you then have electric connections to something on the boom. How do you do connect to the coil and minimize friction and "spring"-type interference to the boom from the connecting wires? I have my own ideas in this area that I think are good, but I'd like to hear what others do for this. > Regards, > > Chris Chapman > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Building a lehman seismometer From: jonfr500@......... Date: Wed, 4 Oct 2006 02:18:59 +0000 Hi In my planning of building a PVC seimsmometer, I also plan to build a Lehma= n seismometer, if I can keep it small enugh. But I need a suggestion for ma= terial and some mesurements and proper drawings before I can start. I also = want to keep the frequancy of the Lehman seismometer around 1Hz. Regards. J=F3n Fr=EDmann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismograph for school From: ChrisAtUpw@....... Date: Tue, 3 Oct 2006 22:54:19 EDT In a message dated 2006/10/04, benbradley@............... writes: > How do you do connect to the coil and minimize friction and "spring"-type > interference to the boom from the connecting wires? Hi Ben, The usual method is to use two small coils, or 'hairpins' maybe 2" long, of the finest insulated copper wire that you can get, which is likely to be 36 gauge, 5 thou, across the lower bearing. If you mount them vertically, they have the least torque. A small torque which is constant will not matter and it is balanced out during levelling. The electrical resistance will be very small compared to that of the coil. If you use wire like Beldsol, it has polyurethane insulation. You wrap it around the terminal post, apply a hot soldering iron and resin cored solder and the insulation just melts. You do not need to 'strip' the wire. Regards, Chris Chapman In a me= ssage dated 2006/10/04, benbradley@............... writes:

How do you do connect to the co= il and minimize friction and "spring"-type
interference to the boom from the connecting wires?


Hi Ben,

       The usual method is to use two small co= ils, or 'hairpins' maybe 2" long, of the finest insulated copper wire that y= ou can get, which is likely to be 36 gauge, 5 thou, across the lower bearing= .. If you mount them vertically, they have the least torque. A small torqu= e which is constant will not matter and it is balanced out during levell= ing. The electrical resistance will be very small compared to that of the co= il. If you use wire like Beldsol, it has polyurethane insulation. You wrap i= t around the terminal post, apply a hot soldering iron and resin cored solde= r and the insulation just melts. You do not need to 'strip' the wire.

       Regards,

       Chris Chapman Subject: Re: Building a lehman seismometer From: ChrisAtUpw@....... Date: Tue, 3 Oct 2006 23:23:14 EDT In a message dated 2006/10/04, jonfr500@......... writes: > I also plan to build a Lehman seismometer, if I can keep it small enough. > But I need a suggestion for material and some mesurements and proper drawings > before I can start. I also want to keep the frequency of the Lehman > seismometer around 1Hz. Hi Jon, The whole point about a Lehman type seismometer is that you take a pedulum which would have a period of about 1.3 to 1.5 sec if mounted vertically and extend the period to maybe 20 sec. The sensor will respond from 20 sec to the 10 Hz of your amplifier filter. I suspect that an arm of between 45 and 60 cm would be fine for you. Don't try to make it smaller. This should pick up your seismic signals very well. I make a T / L frame with U channel Al with 5 mm Al plate for the corner supports. I don't know what materials are available to you. You can use 50 x 25 mm, but I prefer 75 x 25 mm section. Regards, Chris Chapman In a me= ssage dated 2006/10/04, jonfr500@......... writes:

I also plan to build a Lehman s= eismometer, if I can keep it small enough. But I need a suggestion for mater= ial and some mesurements and proper drawings before I can start. I also want= to keep the frequency of the Lehman seismometer around 1Hz.

Hi Jon,

       The  whole point about a Lehman ty= pe seismometer is that you take a pedulum which would have a period of about= 1.3 to 1.5 sec if mounted vertically and extend the period to maybe 20 sec.= The sensor will respond from 20 sec to the 10 Hz of your amplifier filter.=20= I suspect that an arm of between 45 and 60 cm would be fine for you. Don't t= ry to make it smaller. This should pick up your seismic signals very well.
       I make a T / L frame with U channel Al=20= with 5 mm Al plate for the corner supports. I don't know what materials are=20= available to you. You can use 50 x 25 mm, but I prefer 75 x 25 mm section.
       Regards,

       Chris Chapman Subject: ebay auction From: Bob Barns royb1@........... Date: Wed, 04 Oct 2006 09:50:06 -0400 INTENSITRON Earthquake Intensity Computer (seismometer) Item number: 160037359005 ends Oct 8 Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Building a lehman seismometer From: "tchannel" tchannel@.............. Date: Wed, 4 Oct 2006 11:00:34 -0600 Hi Everyone, I did find some 38 gauge magnet wire, but thought you = might like to see this on ebay. 37 gauge Item number: 290035960569 one = pound. Thanks, Ted ----- Original Message ----- From: ChrisAtUpw@.......... To: psn-l@................. Sent: Tuesday, October 03, 2006 9:23 PM Subject: Re: Building a lehman seismometer In a message dated 2006/10/04, jonfr500@......... writes: I also plan to build a Lehman seismometer, if I can keep it small = enough. But I need a suggestion for material and some mesurements and = proper drawings before I can start. I also want to keep the frequency of = the Lehman seismometer around 1Hz. Hi Jon,=20 The whole point about a Lehman type seismometer is that you = take a pedulum which would have a period of about 1.3 to 1.5 sec if = mounted vertically and extend the period to maybe 20 sec. The sensor = will respond from 20 sec to the 10 Hz of your amplifier filter. I = suspect that an arm of between 45 and 60 cm would be fine for you. Don't = try to make it smaller. This should pick up your seismic signals very = well. I make a T / L frame with U channel Al with 5 mm Al plate for = the corner supports. I don't know what materials are available to you. = You can use 50 x 25 mm, but I prefer 75 x 25 mm section. Regards, Chris Chapman
Hi Everyone,  I did find some 38 = gauge magnet=20 wire, but thought you might like to see this on ebay.  37 gauge = Item=20 number: 290035960569 one pound.
 
Thanks, Ted
 
----- Original Message ----- = From: ChrisAtUpw@.......
Sent: Tuesday, October 03, 2006 = 9:23=20 PM
Subject: Re: Building a lehman=20 seismometer

In a=20 message dated 2006/10/04, jonfr500@......... = writes:

I also plan to build a Lehman seismometer, if I can keep = it=20 small enough. But I need a suggestion for material and some = mesurements and=20 proper drawings before I can start. I also want to keep the = frequency of the=20 Lehman seismometer around 1Hz.


Hi Jon,=20

       The  whole point = about a=20 Lehman type seismometer is that you take a pedulum which would have a = period=20 of about 1.3 to 1.5 sec if mounted vertically and extend the period to = maybe=20 20 sec. The sensor will respond from 20 sec to the 10 Hz of your = amplifier=20 filter. I suspect that an arm of between 45 and 60 cm would be fine = for you.=20 Don't try to make it smaller. This should pick up your seismic signals = very=20 well.

       I make a T / L frame = with U=20 channel Al with 5 mm Al plate for the corner supports. I don't know = what=20 materials are available to you. You can use 50 x 25 mm, but I prefer = 75 x 25=20 mm section.

      =20 Regards,

       Chris Chapman=20
Subject: Maine US Quakes From: "Thomas Dick" dickthomas01@............. Date: Thu, 5 Oct 2006 09:36:31 -0500 Thsi in our local paper this morning ... I quote Bar Harbor, Maine title of article "Water table drops after quake" Moinday's earthquake lowered the water level by 3 1/2 feet at one lo0cation in a national park but wasn't expected to hurt the water supply, officials said. By Wednesday, the water level was still falling but beginning to level off, said Gregory Stewart, a hydrologist water level was observed at one of the ageny's monitoring wells in Acadia National Park. The earthquake registered a magnitude of 3.9 and followed quakes with magnitudes of 3.5 and 2.5 on Sept. 22 and 26. and Maine was one place they felt safe putting atomic generating plants! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Building a lehman seismometer From: "tchannel" tchannel@.............. Date: Thu, 5 Oct 2006 09:46:28 -0600 Hi Chris, A few questions: 1 Does your coil and damper assemblies just set on the aluminum base, = free to move for adjustment, or are they fixed to the base? 2 You cleaned the plates, which hold the magnets, and then painted the = exterior, but not the surface the magnets touch. Would the paint = interfere with something on that surface? 3 This is a hard question. Assuming I have finished my sensor, and = leveled it, what is the procedure for adjusting the period? I know the = target angle. I would guess one would have to start at that point, with the base = level, the pendulum level, and everything plumb. You mentioned the formula for determining the angle of the hinge, I have = that information. Not knowing the correct procedure, and not being able = to measure that small of an angle, I would have converted the angle into = a decimal of inches, and measured the difference from the top hinge to = the bottom hinge. Maybe you could walk me through this procedure? 4 I get confused with many of these terms, so I hope you understand this = question. If the target period is say 10 seconds, would the arm move, = when pulled 10mm, verrrrrrrrrry slowly, taking 10 seconds to complete = one cycle? 5 After it is leveled and the period is set, Is it then that you can = check the damp, by moving the arm 10mm and releasing it? I know what an underdamped situation would look like. But is there way = to tell if it is over damped? Thanks, Ted ----- Original Message -----=20 From: ChrisAtUpw@.......... To: psn-l@................. Sent: Tuesday, October 03, 2006 9:23 PM Subject: Re: Building a lehman seismometer In a message dated 2006/10/04, jonfr500@......... writes: I also plan to build a Lehman seismometer, if I can keep it small = enough. But I need a suggestion for material and some mesurements and = proper drawings before I can start. I also want to keep the frequency of = the Lehman seismometer around 1Hz. Hi Jon,=20 The whole point about a Lehman type seismometer is that you = take a pedulum which would have a period of about 1.3 to 1.5 sec if = mounted vertically and extend the period to maybe 20 sec. The sensor = will respond from 20 sec to the 10 Hz of your amplifier filter. I = suspect that an arm of between 45 and 60 cm would be fine for you. Don't = try to make it smaller. This should pick up your seismic signals very = well. I make a T / L frame with U channel Al with 5 mm Al plate for = the corner supports. I don't know what materials are available to you. = You can use 50 x 25 mm, but I prefer 75 x 25 mm section. Regards, Chris Chapman
Hi Chris,   A few = questions:
 
1 Does your coil and damper = assemblies just=20 set on the aluminum base, free to move for adjustment, or are they fixed = to the=20 base?
 
2 You cleaned the plates, which = hold the=20 magnets, and then painted the exterior, but not the surface the magnets=20 touch.  Would the paint interfere with something on that=20 surface?
 
3 This is a hard question.  = Assuming I=20 have finished my sensor, and leveled it, what is the procedure for = adjusting the=20 period?  I know the target angle.
I would guess one would have to start = at that=20 point, with the base level, the pendulum level, and everything=20 plumb.
You mentioned the formula for = determining the angle=20 of the hinge, I have that information.  Not knowing the correct = procedure,=20 and not being able to measure that small of an angle, I would have = converted the=20 angle into a decimal of inches, and measured the difference from the top = hinge=20 to the bottom hinge.  Maybe you could walk me through this=20 procedure?
 
4 I = get confused=20 with many of these terms, so I hope you understand this question.  = If the=20 target period is say 10 seconds, would the arm move, when pulled 10mm,=20 verrrrrrrrrry slowly, taking 10 seconds to complete one = cycle?
 
5  After it is leveled and the = period is set,=20 Is it then that you can check the damp, by moving the arm 10mm and = releasing=20 it?
I know what an underdamped situation = would look=20 like.  But is there way to tell if it is over damped?
 
Thanks, Ted
 
 
 
 
----- Original Message -----
From:=20 ChrisAtUpw@.......
Sent: Tuesday, October 03, 2006 = 9:23=20 PM
Subject: Re: Building a lehman=20 seismometer

In a=20 message dated 2006/10/04, jonfr500@......... = writes:

I also plan to build a Lehman seismometer, if I can keep = it=20 small enough. But I need a suggestion for material and some = mesurements and=20 proper drawings before I can start. I also want to keep the = frequency of the=20 Lehman seismometer around 1Hz.

Hi Jon,=20

       The  whole point = about a=20 Lehman type seismometer is that you take a pedulum which would have a = period=20 of about 1.3 to 1.5 sec if mounted vertically and extend the period to = maybe=20 20 sec. The sensor will respond from 20 sec to the 10 Hz of your = amplifier=20 filter. I suspect that an arm of between 45 and 60 cm would be fine = for you.=20 Don't try to make it smaller. This should pick up your seismic signals = very=20 well.

       I make a T / L frame = with U=20 channel Al with 5 mm Al plate for the corner supports. I don't know = what=20 materials are available to you. You can use 50 x 25 mm, but I prefer = 75 x 25=20 mm section.

      =20 Regards,

       Chris Chapman=20 Subject: Re: Building a lehman seismometer From: ChrisAtUpw@....... Date: Thu, 5 Oct 2006 15:26:42 EDT In a message dated 2006/10/05, tchannel@.............. writes: > 1 Does your coil and damper assemblies just set on the aluminum base, free > to move for adjustment, or are they fixed to the base? Hi Ted, My arm has a support wire fixture and then a mass right at the end of the arm. The support fixture carries a damping tongue in the direction of the hinge and a coil on the mass side. Both the sensor and damper magnets slide on the base strip, for mounting and adjustment of their position. They have small guide strips underneath which hold them parallel. > 2 You cleaned the plates, which hold the magnets, and then painted the > exterior, but not the surface the magnets touch. Would the paint interfere with > something on that surface? I suggest that you paint everything with Hammerite or similar, but try to get it smooth and level. I etch coated the magnet position with phosphoric acid, allowed it to react and dry overnight and then put CL anticorrosion car grease on it. I was not certain that I could get enough damping initially, but I found that I could overdamp the system quite easily, so I increased the damper magnet spacing. > 3 This is a hard question. Assuming I have finished my sensor, and levelled > it, what is the procedure for adjusting the period? Maybe you could walk me > through this procedure? You first lower the base plate / strip at the mass end. Then you mount the arm and make any necessary solder connections for the coil wiring. Then you put the magnet units on the base and adjust the top wire so that both the coil and the damping plate are central within the magnet spacings. The first time, you may need to make adjustments of the magnet block heights, so that the arm is parallel to the base. Then you slide the damper free and adjust the cross levels so that the arm is stable in the central position. If you can't get a stable central position, you need to adjust the suspension so that the top hinge is nearer the mass end - or the bottom fitting is further away. You may mark the end of the arm with an inkline and also put a central mark on the base. You deflect the arm and time a swing. It may be about 5 sec initially. Then you slowly raise the base at the mass end of the arm with the adjusting screw, testing to determine the period, until you get the period you want. As the period is lengthened, you will probably need to trim the cross level slightly. Then you slide the damping magnet over edge of the tongue, deflect the arm 10 mm and release it. It may help to stick a bit of graph paper to the base to be able the measure the position of the damping block. 0.7 damping is obtained when the arm swings 0.5 mm past the zero position and then falls back again. The amount of damping decreases as the set period increases, so it needs to be easily adjustable. If the critical position is obtained with the tongue less that half covering the magnets, increase the damper magnet spacing. > 4 I get confused with many of these terms, so I hope you understand this > question. If the target period is say 10 seconds, would the arm move, when > pulled 10mm, very slowly, taking 10 seconds to complete one cycle? That is correct. Assuming that the arm is not damped, you deflect it and then release it. It takes 2.5 sec to get to zero, overshoots and comes back to zero in 5 sec, overshoots again and comes back to zero from the initial direction in another 5 sec. Total 5 + 5 = 10 sec. The period is the time for one complete oscillation cycle. You want at least twice this. > 5 After it is leveled and the period is set, Is it then that you can check > the damp, by moving the arm 10mm and releasing it? Correct, you set up the period first and then you slide the damper further over the tongue in small steps until it is just a bit under critical. > I know what an underdamped situation would look like. But is there way > to tell if it is over damped? As you increase the damping from zero, the time that the arm takes to fall back through / to the balance position increases slightly. If you overdamp the arm, it never swings through the zero position and the more you damp it, the longer it takes to get there. Look for the arm swinging just past the zero line, but without another oscillation. Regards, Chris Chapman In a me= ssage dated 2006/10/05, tchannel@.............. writes:

1 Does your coil and damper ass= emblies just set on the aluminum base, free to move for adjustment, or are t= hey fixed to the base?


Hi Ted,

       My arm has a support wire fixture and t= hen a mass right at the end of the arm.
       The support fixture carries a damping t= ongue in the direction of the hinge and a coil on the mass side.
       Both the sensor and damper magnets slid= e on the base strip, for mounting and adjustment of their position. They hav= e small guide strips underneath which hold them parallel.  

2 You cleaned the plates, whic= h hold the magnets, and then painted the exterior, but not the surface the m= agnets touch.  Would the paint interfere with something on that surface= ?


       I suggest that you paint everything wi= th Hammerite or similar, but try to get it smooth and level. I etch coated t= he magnet position with phosphoric acid, allowed it to react and dry overnig= ht and then put CL anticorrosion car grease on it. I was not certain that I=20= could get enough damping initially, but I found that I could overdamp the sy= stem quite easily, so I increased the damper magnet spacing.

3 This is a hard question. Ass= uming I have finished my sensor, and levelled it, what is the procedure for=20= adjusting the period? Maybe you could walk me through this procedure?=

       You first lower the base plate / strip= at the mass end. Then you mount the arm and make any necessary solder conne= ctions for the coil wiring. Then you put the magnet units on the base and ad= just the top wire so that both the coil and the damping plate are central wi= thin the magnet spacings. The first time, you may need to make adjustments o= f the magnet block heights, so that the arm is parallel to the base.
       Then you slide the damper free and adju= st the cross levels so that the arm is stable in the central position. If yo= u can't get a stable central position, you need to adjust the suspension so=20= that the top hinge is nearer the mass end - or the bottom fitting is further= away. You may mark the end of the arm with an inkline and also put a centra= l mark on the base. You deflect the arm and time a swing. It may be about 5=20= sec initially. Then you slowly raise the base at the mass end of the arm wit= h the adjusting screw, testing to determine the period, until you get the pe= riod you want. As the period is lengthened, you will probably need to trim t= he cross level slightly.
       Then you slide the damping magnet o= ver edge of the tongue, deflect the arm 10 mm and release it. It may help to= stick a bit of graph paper to the base to be able the measure the position=20= of the damping block. 0.7 damping is obtained when the arm swings 0.5 mm pas= t the zero position and then falls back again.
       The amount of damping decreases as the=20= set period increases, so it needs to be easily adjustable. If the critical p= osition is obtained with the tongue less that half covering the magnets, inc= rease the damper magnet spacing.

4 I get confused with many of=20= these terms, so I hope you understand this question.  If the target per= iod is say 10 seconds, would the arm move, when pulled 10mm, very slowly, ta= king 10 seconds to complete one cycle?


       That is correct. Assuming that the arm= is not damped, you deflect it and then release it. It takes 2.5 sec to get=20= to zero, overshoots and comes back to zero in 5 sec, overshoots again and co= mes back to zero from the initial direction in another 5 sec. Total 5 + 5=20= =3D 10 sec. The period is the time for one complete oscillation cycle. You w= ant at least twice this.

5  After it is leveled an= d the period is set, Is it then that you can check the damp, by moving the a= rm 10mm and releasing it?


       Correct, you set up the period first a= nd then you slide the damper further over the tongue in small steps until it= is just a bit under critical.

    I know what= an underdamped situation would look like.  But is there way to tell if= it is over damped?


       As you increase the damping from zero,=20= the time that the arm takes to fall back through / to the balance position i= ncreases slightly. If you overdamp the arm, it never swings through the zero= position and the more you damp it, the longer it takes to get there. Look f= or the arm swinging just past the zero line, but without another oscillation= ..

       Regards,

       Chris Chapman Subject: Sensor magnet and coil design From: Bobhelenmcclure@....... Date: Thu, 5 Oct 2006 16:11:35 EDT I submitting this note in order to give others the benefits of my own sometimes trial-and-error efforts to build a seismic sensor. I am sure that Chris Chapman will continue to contribute, as well. Both Chris Chapman and I favor the use of Neodymium Iron Boron magnets arranged in a four-pole structure for generating the magnetic field needed for velocity sensing and damping in seismic sensors. The magnets are powerful, relatively cheap, and easily obtained. The magnets I favor are block magnets, 6 mm thick, 18 mm wide, and 50 mm long. They are magnetized in the thickness direction and are of the composition known as N38. They have a coercive force of about 12,000 Oersteds (CGS units), corresponding to 1.2 Teslas in the SI system. Construction of a four-pole magnet assembly is very simple, but also very hazardous. These magnets are attracted to steel and to each other with a force of about 57 pounds per square inch, and any skin caught between them can be badly nipped. You must keep loose magnets very far away from steel or each other and wear heavy leather work gloves when handling them. The magnets are brittle, and will break if they crash together or with steel. The pole plates are mild steel, thick enough to carry the flux of the magnetic circuit. More on that later. One of the plates must have clearance holes for 3/16" bolts, one hole in each corner. The plates, for the above magnet dimensions, should measure two inches by at least three inches. Slide two magnets onto each plate, with opposite poling on each plate. When you have one magnet in position on a plate, carefully hold the second magnet above the first. You will feel either an attraction or a repulsion of the second magnet toward the one on the plate. Make sure the force is repulsive, then slide the second magnet into place beside the first. When the magnets are positioned on each plate, make a wooden or plastic shim somewhat thinner than the final magnet gap you intend to use. I would use a shim about six inches long and the same width as the paired magnets, which would be about 1.5 inches for the example. With the shim covering the magnets of one plate, hold the second plate over it, getting no closer than enough to determine if the force between them is attractive or repulsive. The correct alignment is indicated by an attractive force. You now place the upper plate (magnets down) on the shim at one end of the lower plate and slide the upper plate and magnets up over the lower magnets. You now have a sandwich of upper and lower assemblies tightly squeezing the shim in between. Place four bolts in the plate with the holes. Note than these bolts are used to hold the plates apart, not together. Use the bolts to jack the plates apart to get the desired gap spacing, and then you can withdraw the shim. If each of your plates have clearance holes drilled in them, you will need two nuts for each screw. Now it is time to discuss what field strength you get, and what thickness of steel is required. Suppose for my example using 6 mm thick magnets, I use a gap of 6 mm. The resulting distance between plates is 18 mm, 12 mm filled with magnet, and 6 mm with air. I call the ratio of total magnet thickness to total plate separation the filling factor. To a first approximation, the gap field the coercive force of the magnetic material multiplied by the filling factor. In this example, the coercive force is 12 KOe and the filling factor is 2/3, so the gap field is 8 KOe. The accuracy of this estimate depends on the magnet width compared to the gap size. If the gap becomes appreciable compared to the width, you will get more fringing field and less-than-expected gap field. I have written a program that solves LaPlace's equation by iteration which lets me estimate more exactly what the penalty is for any geometry. For my example magnet structure, I use 1/4 inch thick steel plates. I find that there is a very slight saturation of the plates in the region between magnet pairs. When I use 24 mm wide magnets, there is a lot of saturation and a lot of external stray field around the whole assembly. I have to put steel side plates on the assembly to eliminate the saturation and the stray field. Steel can carry a flux density of about 20 to 24 KOe without saturation. Without saturation, the magnetic circuit of a 4-pole structure consists of a closed rectangular flux path, with lines traveling through magnets, gaps, and steel. The steel must carry the same total number of lines of flux as the gap and magnets. The number of lines is proportional to the gap flux density multiplied by the magnet width. In the example of 8 KOe and 18 mm width, this corresponds to 8,000 times 1.8, or 14,000 lines per lineal centimeter of magnet structure. The quarter-inch-thick steel (0.625 cm) must carry a flux density of 22,000 KOe. It does so, barely. The next topic is coil design. By following the above magnet assembly design principles, you know the approximate gap field, so by also knowing the magnet length you will be able to estimate the number of coil turns you will need to achieve a given output sensitivity in volts per meter per second. If the end loops of the coil extend beyond the ends of the magnet, each turn is immersed in a total field length of twice the magnet length. In the example design, the magnet length is 50 mm, so L per turn is 0.1 m. The output voltage generated by the moving coil is Volts = B * N * L * Vel, where B is field strength in Teslas, N is number of turns, L is length per turn in the field, and Vel is velocity in meters per second. One Tesla corresponds to 10,000 Oersteds. Suppose n = 1100, B = 0.8 Tesla, and L = 0.1 meter. Then Volts/Vel = 0.8 * 1100 * 0.1 = 88 v-s/m, which is a good number to strive for. A wire size of #38 or less will allow this number of turns to fit comfortably within the gap field cross-section. The coil will have a resistance low enough to permit resistive shunt damping of a pendulum weighing up to a kilogram, in my opinion. My sensors have a pendulum mass of about 0.1Kg, and critical damping is achieved at about 30 kOhms. Since the coil resistance is only 340 Ohms, the shunt damping imposes negligible loss on output sensitivity. Even a kilogram mass would require only about 10% loss of output using shunt damping. There is one significant complication to this type of magnet and coil design, having to do with the fact that pure copper is diamagnetic, and coil and its pendulum are subject to forces other than the desired restoring force of a garden gate pendulum. In the example design this diamagnetic force is a decentering force, making it very difficult to adjust the sensor to a state of stable long period equilibrium. I reduce this effect by essentially potting the coil in acrylic plastic, which is also diamagnetic, and having the boundaries of the plastic extend well outside the edges of the magnetic field. Using a heavier pendulum would be of great benefit, as well. Bob McClure
  I submitting this note in order to give others the benefits of m= y=20 own sometimes trial-and-error efforts to build a seismic sensor. I am sure t= hat=20 Chris Chapman will continue to contribute, as well.
 
  Both Chris Chapman and I favor the use of Neodymium Iron Boron=20 magnets arranged in a four-pole structure for generating the magnetic field=20 needed for velocity sensing and damping in seismic sensors. The magnets are=20 powerful, relatively cheap, and easily obtained. The magnets I favor ar= e=20 block magnets, 6 mm thick, 18 mm wide, and 50 mm long. They are magnetized i= n=20 the thickness direction and are of the composition known as N38. They have a= =20 coercive force of about 12,000 Oersteds (CGS units), corresponding to 1.2 Te= slas=20 in the SI system.
 
  Construction of a four-pole magnet assembly is very simple, but=20= also=20 very hazardous. These magnets are attracted to steel and to each other with=20= a=20 force of about 57 pounds per square inch, and any skin caught between them c= an=20 be badly nipped. You must keep loose magnets very far away from steel or eac= h=20 other and wear heavy leather work gloves when handling them. The magnets are= =20 brittle, and will break if they crash together or with steel. The pole plate= s=20 are mild steel, thick enough to carry the flux of the magnetic circuit. More= on=20 that later. One of the plates must have clearance holes for 3/16" bolts, one= =20 hole in each corner. The plates, for the above magnet dimensions, should mea= sure=20 two inches by at least three inches.
 
  Slide two magnets onto each plate, with opposite poling on each=20 plate. When you have one magnet in position on a plate, carefully hold the=20 second magnet above the first. You will feel either an attraction or a repul= sion=20 of the second magnet toward the one on the plate. Make sure the force is=20 repulsive, then slide the second magnet into place beside the first. When th= e=20 magnets are positioned on each plate, make a wooden or plastic shim somewhat= =20 thinner than the final magnet gap you intend to use. I would use a shim abou= t=20 six inches long and the same width as the paired magnets, which would be abo= ut=20 1.5 inches for the example. With the shim covering the magnets of one plate,= =20 hold the second plate over it, getting no closer than enough to determine if= the=20 force between them is attractive or repulsive. The correct alignment is=20 indicated by an attractive force. You now place the upper plate (magnets dow= n)=20 on the shim at one end of the lower plate and slide the upper plate and magn= ets=20 up over the lower magnets. You now have a sandwich of upper and lower assemb= lies=20 tightly squeezing the shim in between.
 
  Place four bolts in the plate with the holes. Note than these bo= lts=20 are used to hold the plates apart, not together. Use the bolts to jack the=20 plates apart to get the desired gap spacing, and then you can withdraw the s= him.=20 If each of your plates have clearance holes drilled in them, you will need t= wo=20 nuts for each screw.
 
  Now it is time to discuss what field strength you get, and what=20 thickness of steel is required. Suppose for my example using 6 mm thick magn= ets,=20 I use a gap of 6 mm. The resulting distance between plates is 18 mm, 12 mm=20 filled with magnet, and 6 mm with air. I call the ratio of total magnet=20 thickness to total plate separation the filling factor. To a first=20 approximation, the gap field the coercive force of the magnetic material=20 multiplied by the filling factor. In this example, the coercive force is 12=20= KOe=20 and the filling factor is 2/3, so the gap field is 8 KOe. The accuracy of th= is=20 estimate depends on the magnet width compared to the gap size. If the gap=20 becomes appreciable compared to the width, you will get more fringing field=20= and=20 less-than-expected gap field. I have written a program that solves LaPlace's= =20 equation by iteration which lets me estimate more exactly what the penalty i= s=20 for any geometry.
 
  For my example magnet structure, I use 1/4 inch thick steel plat= es.=20 I find that there is a very slight saturation of the plates in the region=20 between magnet pairs. When I use 24 mm wide magnets, there is a lot of=20 saturation and a lot of external stray field around the whole assembly. I ha= ve=20 to put steel side plates on the assembly to eliminate the saturation and the= =20 stray field. Steel can carry a flux density of about 20 to 24 KOe without=20 saturation. Without saturation, the magnetic circuit of a 4-pole structure=20 consists of a closed rectangular flux path, with lines traveling through=20 magnets, gaps, and steel. The steel must carry the same total number of line= s of=20 flux as the gap and magnets. The number of lines is proportional to the gap=20= flux=20 density multiplied by the magnet width. In the example of 8 KOe and 18 mm wi= dth,=20 this corresponds to 8,000 times 1.8, or 14,000 lines per lineal centime= ter=20 of magnet structure. The quarter-inch-thick steel (0.625 cm) must carry a fl= ux=20 density of 22,000 KOe. It does so, barely.
 
  The next topic is coil design. By following the above magnet=20 assembly design principles, you know the approximate gap field, so by also=20 knowing the magnet length you will be able to estimate the number of coil tu= rns=20 you will need to achieve a given output sensitivity in volts per meter per=20 second. If the end loops of the coil extend beyond the ends of the magnet, e= ach=20 turn is immersed in a total field length of twice the magnet length. In the=20 example design, the magnet length is 50 mm, so L per turn is 0.1 m.
 
  The output voltage generated by the moving coil is Volts =3D B *= N * L=20 * Vel, where B is field strength in Teslas, N is number of turns, L is lengt= h=20 per turn in the field, and Vel is velocity in meters per second. One Tesla=20 corresponds to 10,000 Oersteds. Suppose n =3D 1100, B =3D 0.8 Tesla, and L=20= =3D 0.1=20 meter. Then Volts/Vel =3D 0.8 * 1100 * 0.1 =3D 88 v-s/m, which is a good num= ber to=20 strive for.
 
  A wire size of #38 or less will allow this number of turns to fi= t=20 comfortably within the gap field cross-section. The coil will have a resista= nce=20 low enough to permit resistive shunt damping of a pendulum weighing up to a=20 kilogram, in my opinion. My sensors have a pendulum mass of about 0.1Kg, and= =20 critical damping is achieved at about 30 kOhms. Since the coil resistance is= =20 only 340 Ohms, the shunt damping imposes negligible loss on output sensitivi= ty.=20 Even a kilogram mass would require only about 10% loss of output using shunt= =20 damping.
 
  There is one significant complication to this type of magnet and= =20 coil design, having to do with the fact that pure copper is diamagnetic, and= =20 coil and its pendulum are subject to forces other than the desired restoring= =20 force of a garden gate pendulum. In the example design this diamagnetic forc= e is=20 a decentering force, making it very difficult to adjust the sensor to a stat= e of=20 stable long period equilibrium. I reduce this effect by essentially potting=20= the=20 coil in acrylic plastic, which is also diamagnetic, and having the boundarie= s of=20 the plastic extend well outside the edges of the magnetic field. Using a hea= vier=20 pendulum would be of great benefit, as well.
 
Bob McClure
 Subject: Re: Building a lehman seismometer From: "tchannel" tchannel@.............. Date: Thu, 5 Oct 2006 15:50:06 -0600 Thanks, Chris for your reply. Most helpful I am in the process of building a sensor bases on your prototype, and = great drawings. I have most of the parts located, again with your help = and others on the mailing list. I will send pictures as I go along, if = you like, and if you tell me how to send them. I regards to the angle between the bottom and top hinge, a fraction of a = degree, how do you measure for that? Or do you adjust and measure the = period, instead? Chris, I see on your drawing you did not need to brace the vertical arm = of your device. Looks very strong. How did you attach that vertical to = the cross member? Many Thanks, Ted ----- Original Message -----=20 From: ChrisAtUpw@.......... To: psn-l@................. Sent: Thursday, October 05, 2006 1:26 PM Subject: Re: Building a lehman seismometer In a message dated 2006/10/05, tchannel@.............. writes: 1 Does your coil and damper assemblies just set on the aluminum = base, free to move for adjustment, or are they fixed to the base? Hi Ted, My arm has a support wire fixture and then a mass right at the = end of the arm. The support fixture carries a damping tongue in the direction = of the hinge and a coil on the mass side. Both the sensor and damper magnets slide on the base strip, for = mounting and adjustment of their position. They have small guide strips = underneath which hold them parallel. =20 2 You cleaned the plates, which hold the magnets, and then painted = the exterior, but not the surface the magnets touch. Would the paint = interfere with something on that surface? I suggest that you paint everything with Hammerite or similar, = but try to get it smooth and level. I etch coated the magnet position = with phosphoric acid, allowed it to react and dry overnight and then put = CL anticorrosion car grease on it. I was not certain that I could get = enough damping initially, but I found that I could overdamp the system = quite easily, so I increased the damper magnet spacing. 3 This is a hard question. Assuming I have finished my sensor, and = levelled it, what is the procedure for adjusting the period? Maybe you = could walk me through this procedure? You first lower the base plate / strip at the mass end. Then = you mount the arm and make any necessary solder connections for the coil = wiring. Then you put the magnet units on the base and adjust the top = wire so that both the coil and the damping plate are central within the = magnet spacings. The first time, you may need to make adjustments of the = magnet block heights, so that the arm is parallel to the base. Then you slide the damper free and adjust the cross levels so = that the arm is stable in the central position. If you can't get a = stable central position, you need to adjust the suspension so that the = top hinge is nearer the mass end - or the bottom fitting is further = away. You may mark the end of the arm with an inkline and also put a = central mark on the base. You deflect the arm and time a swing. It may = be about 5 sec initially. Then you slowly raise the base at the mass end = of the arm with the adjusting screw, testing to determine the period, = until you get the period you want. As the period is lengthened, you will = probably need to trim the cross level slightly. Then you slide the damping magnet over edge of the tongue, = deflect the arm 10 mm and release it. It may help to stick a bit of = graph paper to the base to be able the measure the position of the = damping block. 0.7 damping is obtained when the arm swings 0.5 mm past = the zero position and then falls back again. The amount of damping decreases as the set period increases, so = it needs to be easily adjustable. If the critical position is obtained = with the tongue less that half covering the magnets, increase the damper = magnet spacing.=20 4 I get confused with many of these terms, so I hope you understand = this question. If the target period is say 10 seconds, would the arm = move, when pulled 10mm, very slowly, taking 10 seconds to complete one = cycle? That is correct. Assuming that the arm is not damped, you = deflect it and then release it. It takes 2.5 sec to get to zero, = overshoots and comes back to zero in 5 sec, overshoots again and comes = back to zero from the initial direction in another 5 sec. Total 5 + 5 = =3D 10 sec. The period is the time for one complete oscillation cycle. = You want at least twice this. 5 After it is leveled and the period is set, Is it then that you = can check the damp, by moving the arm 10mm and releasing it? Correct, you set up the period first and then you slide the = damper further over the tongue in small steps until it is just a bit = under critical. I know what an underdamped situation would look like. But is = there way to tell if it is over damped? As you increase the damping from zero, the time that the arm = takes to fall back through / to the balance position increases slightly. = If you overdamp the arm, it never swings through the zero position and = the more you damp it, the longer it takes to get there. Look for the arm = swinging just past the zero line, but without another oscillation. Regards, Chris Chapman
Thanks, Chris for your reply. Most=20 helpful
 
   I am in the process of = building a=20 sensor bases on your prototype, and great drawings.   I have = most of=20 the parts located, again with your help and others on the mailing = list.  I=20 will send pictures as I go along, if you like, and if you tell me how to = send=20 them.
 
I regards to the angle between the = bottom and top=20 hinge, a fraction of a degree, how do you measure for that? Or do you = adjust and=20 measure the period, instead?
 
Chris, I see on your drawing you did = not need to=20 brace the vertical arm of your device. Looks very strong.  How did = you=20 attach that vertical to the cross member?
 
Many Thanks, Ted
 
 
----- Original Message -----
From:=20 ChrisAtUpw@.......
Sent: Thursday, October 05, = 2006 1:26=20 PM
Subject: Re: Building a lehman=20 seismometer

In a=20 message dated 2006/10/05, tchannel@..............=20 writes:

1 Does your coil and damper assemblies just set on the = aluminum=20 base, free to move for adjustment, or are they fixed to the=20 base?


Hi=20 Ted,

       My arm has a support = wire=20 fixture and then a mass right at the end of the=20 arm.
       The support fixture = carries a=20 damping tongue in the direction of the hinge and a coil on the mass=20 side.
       Both the sensor and = damper=20 magnets slide on the base strip, for mounting and adjustment of their=20 position. They have small guide strips underneath which hold them=20 parallel.  

2 You cleaned the plates, which hold the magnets, and = then=20 painted the exterior, but not the surface the magnets touch.  = Would the=20 paint interfere with something on that surface?

       I=20 suggest that you paint everything with Hammerite or similar, but try = to get it=20 smooth and level. I etch coated the magnet position with phosphoric = acid,=20 allowed it to react and dry overnight and then put CL anticorrosion = car grease=20 on it. I was not certain that I could get enough damping initially, = but I=20 found that I could overdamp the system quite easily, so I increased = the damper=20 magnet spacing.

 3 This is a hard question. Assuming I have finished my = sensor,=20 and levelled it, what is the procedure for adjusting the period? = Maybe you=20 could walk me through this procedure?

       You=20 first lower the base plate / strip at the mass end. Then you mount the = arm and=20 make any necessary solder connections for the coil wiring. Then you = put the=20 magnet units on the base and adjust the top wire so that both the coil = and the=20 damping plate are central within the magnet spacings. The first time, = you may=20 need to make adjustments of the magnet block heights, so that the arm = is=20 parallel to the base.
       Then you = slide=20 the damper free and adjust the cross levels so that the arm is stable = in the=20 central position. If you can't get a stable central position, you need = to=20 adjust the suspension so that the top hinge is nearer the mass end - = or the=20 bottom fitting is further away. You may mark the end of the arm with = an=20 inkline and also put a central mark on the base. You deflect the arm = and time=20 a swing. It may be about 5 sec initially. Then you slowly raise the = base at=20 the mass end of the arm with the adjusting screw, testing to determine = the=20 period, until you get the period you want. As the period is = lengthened, you=20 will probably need to trim the cross level slightly.
      =20 Then you = slide the=20 damping magnet over edge of the tongue, deflect the arm 10 mm and = release it.=20 It may help to stick a bit of graph paper to the base to be able the = measure=20 the position of the damping block. 0.7 damping is obtained when the = arm swings=20 0.5 mm past the zero position and then falls back=20 again.
       The amount of damping = decreases=20 as the set period increases, so it needs to be easily adjustable. If = the=20 critical position is obtained with the tongue less that half covering = the=20 magnets, increase the damper magnet spacing.

4 I get confused with many of these terms, so I hope you = understand this question.  If the target period is say 10 = seconds,=20 would the arm move, when pulled 10mm, very slowly, taking 10 seconds = to=20 complete one cycle?

       That is=20 correct. Assuming that the arm is not damped, you deflect it and then = release=20 it. It takes 2.5 sec to get to zero, overshoots and comes back to zero = in 5=20 sec, overshoots again and comes back to zero from the initial = direction in=20 another 5 sec. Total 5 + 5 =3D 10 sec. The period is the time for one = complete=20 oscillation cycle. You want at least twice this.

 5  After it is leveled and the period is set, Is it = then=20 that you can check the damp, by moving the arm 10mm and releasing=20 it?

      =20 Correct, you set up the period first and then you slide the damper = further=20 over the tongue in small steps until it is just a bit under=20 critical.

     I know what an underdamped situation = would=20 look like.  But is there way to tell if it is over=20 damped?

       As = you=20 increase the damping from zero, the time that the arm takes to fall = back=20 through / to the balance position increases slightly. If you overdamp = the arm,=20 it never swings through the zero position and the more you damp it, = the longer=20 it takes to get there. Look for the arm swinging just past the zero = line, but=20 without another = oscillation.

      =20 Regards,

       Chris = Chapman=20 Subject: Re: Building a lehman seismometer From: ChrisAtUpw@....... Date: Thu, 5 Oct 2006 22:59:04 EDT In a message dated 2006/10/05, tchannel@.............. writes: > I am in the process of building a sensor bases on your prototype, and > great drawings. I have most of the parts located, again with your help and > others on the mailing list. I will send pictures as I go along, if you like, and > if you tell me how to send them. Hi Ted, gif or jpg images would do fine to my EMail address. > I regards to the angle between the bottom and top hinge, a fraction of a > degree, how do you measure for that? Or do you adjust and measure the period, > instead? I don't measure it, I calculate it. Then I make the structure so that there is a small amount of adjustment. The axis is defined by the centre of the ball and the edge of the top wire clamp. You vary the slope of the long horizontal baseplate to set the period accurately, using the end adjustment screw, but you keep the arm parallel to the baseplate. > Chris, I see on your drawing you did not need to brace the vertical arm of > your device. Looks very strong. How did you attach that vertical to the > cross member? In my case the bottom of the vertical was milled flat and then the centre sections were milled out ~15 thou so that there were four longitudinal narrow strips about 1/16" wide x 3/4" long at the corners. Then two bolts were put through the cross bar, the long base and threaded into the vertical at the front and back ends. If you don't mill out / file out the centre sections, the clamp force will be at the centre, not at the edges where you want it and it will rock just enough to give trouble. An alternative is to use a flat end and 3 or 4 shim strips. You can also make three point suspensions, or you can glue the vertical to the long base with two part modified acrylic glue. This is strong and tough, unlike epoxy which is brittle. However you have to be very quick as it has a gel time of about a couple of minutes in a warm room. An alternative construction might be to use a 3" dia tube for the vertical? This can be held on either with a central vertical threaded rod and a top plate, or by mounting a 3/4" circular rod horizontally through two holes in the vertical tube, drilling and tapping this and putting a vertical bolt up through the baseplate. You would make three contact strip suspension flats at 120 deg. You can use an SS ball on a carbide flat lower hinge or crossed cylinders. You can buy 1/8" solid tungsten carbide drills from www.Smallparts.com or www.Digikey.com and cut the shanks to length with a carbide disk. Glue one to the head of an SS bolt and the other to the end of the arm with two part modified acrylic glue. I usually file a shallow V first to locate the shank mechanically. Mount the vertical rod or the ball on vertical support and the horizontal rod or the flat on the arm, NOT the other way around! 8 thou Nickel plated piano wire is available for mandolin strings at a music shop. See www.daddario.com Another method of construction which you might wish to consider? In this I used Al alloy U channel, 3" wide x 1" high and three triangular 3/16" to 1/4" thick corner plates at the end T / L joint. The vertical is attached to the long horizontal base with two 5" corner plates and four SS bolts per plate. I use two plain SS washers and a spring washer per bolt to prevent it digging into the softer Al. The open U is on the inside of the 90 deg joint. The cross bar is attached to the outside of the vertical with four bolts and a 7" triangle. It seems to work OK and makes quite a neat job. I bought it cut / chopped to size, from a local metals supermarket. You maybe able to get 2" x 1" U channel from building supplies / DIY. I tend to make things more massive than absolutely necessary. The secret of the rigidity is mostly in the three large triangular joint plates. I tend to use 18" to 24" long tubular arms. 22" gives a 1.5 sec basic pendulum which you can extend by x20 to 30 sec. 3 ft is a bit bulky, but it gives maybe 40 sec or more? You can get compression fittings for most tube. I use 1/2" SS water pipe and brass water fittings, 15mm OD, but the tube may not be widely available? It is light but rigid and non magnetic. Hard drawn Cu or brass are alternatives. You can also buy general purpose brass compression 'engineering' fittings for a wide range of standard pipe sizes, but these may only be available through a few more specialist suppliers and they tend to be more expensive than water fittings. Check on the availabilty of thin wall welded SS water pipe? Regards, Chris Chapman In a me= ssage dated 2006/10/05, tchannel@.............. writes:

   I am in the proces= s of building a sensor bases on your prototype, and great drawings. I have m= ost of the parts located, again with your help and others on the mailing lis= t. I will send pictures as I go along, if you like, and if you tell me how t= o send them.


Hi Ted,

       gif or jpg images would do fine to my E= Mail address.

I regards to the angle between= the bottom and top hinge, a fraction of a degree, how do you measure for th= at? Or do you adjust and measure the period, instead?


       I don't measure it, I calculate it. Th= en I make the structure so that there is a small amount of adjustment. The a= xis is defined by the centre of the ball and the edge of the top wire clamp.= You vary the slope of the long horizontal baseplate to set the period accur= ately, using the end adjustment screw, but you keep the arm parallel to the=20= baseplate.

Chris, I see on your drawing y= ou did not need to brace the vertical arm of your device. Looks very strong.=   How did you attach that vertical to the cross member?

       In my case the bottom of the vertical=20= was milled flat and then the centre sections were milled out ~15 thou so tha= t there were four longitudinal narrow strips about 1/16" wide x 3/4" long at= the corners. Then two bolts were put through the cross bar, the long base a= nd threaded into the vertical at the front and back ends. If you don't mill=20= out / file out the centre sections, the clamp force will be at the centre, n= ot at the edges where you want it and it will rock just enough to give troub= le. An alternative is to use a flat end and 3 or 4 shim strips.
       You can also make three point suspensio= ns, or you can glue the vertical to the long base with two part modified acr= ylic glue. This is strong and tough, unlike epoxy which is brittle. However=20= you have to be very quick as it has a gel time of about a couple of minutes=20= in a warm room.
       An alternative construction might be to= use a 3" dia tube for the vertical? This can be held on either with a centr= al vertical threaded rod and a top plate, or by mounting a 3/4" circular rod= horizontally through two holes in the vertical tube, drilling and tapping t= his and putting a vertical bolt up through the baseplate. You would make thr= ee contact strip suspension flats at 120 deg.
       You can use an SS ball on a carbide fla= t lower hinge or crossed cylinders. You can buy 1/8" solid tungsten carbide=20= drills from www.Smallparts.com or www.Digikey.com and cut the shanks to leng= th with a carbide disk. Glue one to the head of an SS bolt and the other to=20= the end of the arm with two part modified acrylic glue. I usually file a sha= llow V first to locate the shank mechanically. Mount the vertical rod or the= ball on vertical support and the horizontal rod or the flat on the arm, NOT= the other way around! 8 thou Nickel plated piano wire is available for mand= olin strings at a music shop. See www.daddario.com
    Another method of construction which you might wish t= o consider? In this I used Al alloy U channel, 3" wide x 1" high and three t= riangular 3/16" to 1/4" thick corner plates at the end T / L joint. The vert= ical is attached to the long horizontal base with two 5" corner plates and f= our SS bolts per plate. I use two plain SS washers and a spring washer per b= olt to prevent it digging into the softer Al. The open U is on the inside of= the 90 deg joint. The cross bar is attached to the outside of the vertical=20= with four bolts and a 7" triangle. It seems to work OK and makes quite a nea= t job. I bought it cut / chopped to size, from a local metals supermarket. Y= ou maybe able to get 2" x 1" U channel from building supplies / DIY. I tend=20= to make things more massive than absolutely necessary. The secret of the rig= idity is mostly in the three large triangular joint plates.
    I tend to use 18" to 24" long tubular arms. 22" gives a 1= ..5 sec basic pendulum which you can extend by x20 to 30 sec. 3 ft is a bit b= ulky, but it gives maybe 40 sec or more? You can get compression fittings fo= r most tube. I use 1/2" SS water pipe and brass water fittings, 15mm OD, but= the tube may not be widely available? It is light but rigid and non magneti= c. Hard drawn Cu or brass are alternatives. You can also buy general purpose= brass compression 'engineering' fittings for a wide range of standard pipe=20= sizes, but these may only be available through a few more specialist supplie= rs and they tend to be more expensive than water fittings. Check on the avai= labilty of thin wall welded SS water pipe?

    Regards,

    Chris Chapman   
Subject: Re: Sensor magnet and coil design From: ChrisAtUpw@....... Date: Fri, 6 Oct 2006 06:18:14 EDT In a message dated 2006/10/05, Bobhelenmcclure@....... writes: > I submitting this note in order to give others the benefits of my own > sometimes trial-and-error efforts to build a seismic sensor. I am sure that > Chris Chapman will continue to contribute, as well. Hi Bob, Is that meant to be an invitation? > Both Chris Chapman and I favor the use of Neodymium Iron Boron magnets > arranged in a four-pole structure for generating the magnetic field needed for > velocity sensing and damping in seismic sensors. The magnets are powerful, > relatively cheap, and easily obtained. The magnets I favor are block magnets, 6 > mm thick, 18 mm wide, and 50 mm long. They are magnetized in the thickness > direction and are of the composition known as N38. They have a coercive force > of about 12,000 Oersteds (CGS units), corresponding to 1.2 Teslas in the SI > system. > > Construction of a four-pole magnet assembly is very simple, but also very > hazardous. These magnets are attracted to steel and to each other with a > force of about 57 pounds per square inch, and any skin caught between them can be > badly nipped. You must keep loose magnets very far away from steel or each > other and wear heavy leather work gloves when handling them. The magnets are > brittle, and will break if they crash together or with steel. The pole plates > are mild steel, thick enough to carry the flux of the magnetic circuit. More > on that later. One of the plates must have clearance holes for 3/16" bolts, > one hole in each corner. The plates, for the above magnet dimensions, should > measure two inches by at least three inches. So just two of these magnets could probably lift you right off the floor...... You need to plan your assembly, place the magnets over a 3 ft away and be very careful. You will likely sometime get a pinched finger, but with care you can avoid broken bones or a crushed finger joint. I am not being alarmist. You MUST avoid flying magnets! Which is one reason why my designs favour rather smaller magnets and separate the damping and detector functions. The other reason for this is that the systems were designed for school use and you then want to separate out the two functions for educational / demonstration purposes. You already have a large field increase by using the NdFeB magnets in comparison with Alnico and a more sensitive and flexible orientation with the quad magnet arrangement, so you can cut down on total coil turns and still get better performance. This can reduce the resistance and may allow ~more signal amplification. The minimum noise is determined by the input noise impedance characteristics of the opamp. You ~match the coil resistance to this notional resistance figure to get the best performance. In amateur seismic work, you are usually limited in practice by the ambient environmental noise. I prefer zinc plated 1/4" OD set screws to 3/16" OD. Mostly personal choice, but they are a bit more rigid and it also increases the magnetic coupling between the two backing plates, which can carry stray fields. You won't get the total flux of any two magnets matching exactly. > Slide two magnets onto each plate, with opposite poling on each plate. > When you have one magnet in position on a plate, carefully hold the second > magnet above the first. You will feel either an attraction or a repulsion of the > second magnet toward the one on the plate. Make sure the force is repulsive, > then slide the second magnet into place beside the first. When the magnets > are positioned on each plate, make a wooden or plastic shim somewhat thinner > than the final magnet gap you intend to use. I would use a shim about six > inches long and the same width as the paired magnets, which would be about 1.5 > inches for the example. With the shim covering the magnets of one plate, hold > the second plate over it, getting no closer than enough to determine if the > force between them is attractive or repulsive. The correct alignment is > indicated by an attractive force. You now place the upper plate (magnets down) on the > shim at one end of the lower plate and slide the upper plate and magnets up > over the lower magnets. You now have a sandwich of upper and lower assemblies > tightly squeezing the shim in between. If you are doing it this way, I suggest that you attach the plastic shim or preferably a wood block firmly to the first magnet with PVC or gaffer tape. This can help prevent accidents. The forces can be really dangerous. > Place four bolts in the plate with the holes. Note than these bolts are > used to hold the plates apart, not together. Use the bolts to jack the plates > apart to get the desired gap spacing, and then you can withdraw the shim. If > each of your plates have clearance holes drilled in them, you will need two > nuts for each screw. I mount the two magnets on the first block. Then I fit the four bolts with two nuts each. The inner one I do up finger tight, the outer one I leave at ~ 1.5" along the thread. Then I prepare the second plate. I grip the first plate with my hand to prevent the plates getting too close and slide the second plate onto the bolts. With Bob's more powerful magnets, I would use a wood safety block and adhesive tape in place of my hand. I rock this plate till it contacts the nuts and then back off the nuts sequentially about a turn at a time till I get the desired central magnet separation. > Now it is time to discuss what field strength you get, and what thickness > of steel is required. Suppose for my example using 6 mm thick magnets, I use > a gap of 6 mm. The resulting distance between plates is 18 mm, 12 mm filled > with magnet, and 6 mm with air. I call the ratio of total magnet thickness to > total plate separation the filling factor. To a first approximation, the gap > field the coercive force of the magnetic material multiplied by the filling > factor. In this example, the coercive force is 12 KOe and the filling factor > is 2/3, so the gap field is 8 KOe. The accuracy of this estimate depends on > the magnet width compared to the gap size. If the gap becomes appreciable > compared to the width, you will get more fringing field and less-than-expected > gap field. Can you run through the maths and assumptions of this please? > For my example magnet structure, I use 1/4 inch thick steel plates. I > find that there is a very slight saturation of the plates in the region between > magnet pairs. When I use 24 mm wide magnets, there is a lot of saturation > and a lot of external stray field around the whole assembly. I have to put > steel side plates on the assembly to eliminate the saturation and the stray > field. Steel can carry a flux density of about 20 to 24 KOe without saturation. > Without saturation, the magnetic circuit of a 4-pole structure consists of a > closed rectangular flux path, with lines traveling through magnets, gaps, and > steel. The steel must carry the same total number of lines of flux as the gap > and magnets. The number of lines is proportional to the gap flux density > multiplied by the magnet width. In the example of 8 KOe and 18 mm width, this > corresponds to 8,000 times 1.8, or 14,000 lines per lineal centimeter of magnet > structure. The quarter-inch-thick steel (0.625 cm) must carry a flux density > of 22,000 KOe. It does so, barely. Kaye and Laby list the flux density of mild steel at 21.5 k Oer at saturation. If you made the backing plate to just cover the magnets, all the flux would have to go through the centre of the mild steel plate. If you increase the backing plate area, flux can go through this surrounding strip, reducing the overall thickness required, down to about 1/2 minimum, before you have to increase the thickness. I leave a 1/2" wide border around my magnets. The closer the two plates, the greater the field in the gap, so the more flux that the plates have to carry in the critical central area. I put a rounded corner of the magnet just onto the backing plate, rotate it till one edge is on the plate, reduce the angle till maybe 1/4 of the magnet is flat on the plate and then slide the magnet into position. > The next topic is coil design. By following the above magnet assembly > design principles, you know the approximate gap field, so by also knowing the > magnet length you will be able to estimate the number of coil turns you will > need to achieve a given output sensitivity in volts per meter per second. If > the end loops of the coil extend beyond the ends of the magnet, each turn is > immersed in a total field length of twice the magnet length. In the example > design, the magnet length is 50 mm, so L per turn is 0.1 m. > > The output voltage generated by the moving coil is Volts = B * N * L * > Vel, where B is field strength in Teslas, N is number of turns, L is length per > turn in the field, and Vel is velocity in meters per second. One Tesla > corresponds to 10,000 Oersteds. Suppose n = 1100, B = 0.8 Tesla, and L = 0.1 meter. > Then Volts/Vel = 0.8 * 1100 * 0.1 = 88 v-s/m, which is a good number to > strive for. > > A wire size of #38 or less will allow this number of turns to fit > comfortably within the gap field cross-section. The coil will have a resistance low > enough to permit resistive shunt damping of a pendulum weighing up to a > kilogram, in my opinion. My sensors have a pendulum mass of about 0.1Kg, and > critical damping is achieved at about 30 kOhms. Since the coil resistance is only > 340 Ohms, the shunt damping imposes negligible loss on output sensitivity. > Even a kilogram mass would require only about 10% loss of output using shunt > damping. The damping force required also depends on the set period. What period are you using? What effect does this damping current have on the input noise in practice? Can it be significant? Looking at the commonly available lists of insulated wire, the Beldsol polyurethane coated copper wire which you can solder directly without stripping is stocked in sizes down to 36 AWG. You may have to hunt hard / go to professional suppliers for 38 AWG and smaller diameters - higher numbers. The properties of copper wire are listed in the www under AWG copper wire. > There is one significant complication to this type of magnet and coil > design, having to do with the fact that pure copper is diamagnetic, and coil and > its pendulum are subject to forces other than the desired restoring force of > a garden gate pendulum. In the example design this diamagnetic force is a > decentering force, making it very difficult to adjust the sensor to a state of > stable long period equilibrium. I reduce this effect by essentially potting > the coil in acrylic plastic, which is also diamagnetic, and having the > boundaries of the plastic extend well outside the edges of the magnetic field. Using > a heavier pendulum would be of great benefit, as well. Pure copper is diamagnetic, but some copper wire contains a tiny amount of iron, which is strongly paramagnetic. The properties may vary in practice. This is even more of a pest and can result in the coil being attracted by the strong field gradient at the edge of the magnets. With these high fields, you can get the situation where the coil has two stable positions over the edges of the magnets, with an unstable region in between. You may need to check your reel, or your wound coil, or wind a sample coil for a repulsion / attraction test. You may get an even stronger effect when the winding is close to / over the central N/S magnet join. You can reduce this type of problem by increasing the separation between the coil and the edges of the magnets a bit, but this reduces the sensitivity; by limiting the travel of the arm so that the coil does not get too close to the edges of the magnets and by increasing the magnet area and hence the available coil travel, but this may require a thicker backing plate and gives a higher coil resistance. The force on the winding is proportional to H x dH/dr, which falls off very rapidly with increasing r at the edges of the magnet. I appreciate the value of using a wider plastic plate to reduce the change of susceptibility with position. I suspect that it may be important to have a solid plastic core to the coil to reduce forces associated with the cental magnet join. Also, the less copper that is used, the lower the force. Regards, Chris Chapman In a me= ssage dated 2006/10/05, Bobhelenmcclure@....... writes:

  I submitting this note i= n order to give others the benefits of my own sometimes trial-and-error effo= rts to build a seismic sensor. I am sure that Chris Chapman will continue to= contribute, as well.


Hi Bob,

       Is that meant to be an invitation?

  Both Chris Chapman and I= favor the use of Neodymium Iron Boron magnets arranged in a four-pole struc= ture for generating the magnetic field needed for velocity sensing and dampi= ng in seismic sensors. The magnets are powerful, relatively cheap, and easil= y obtained. The magnets I favor are block magnets, 6 mm thick, 18 mm wide, a= nd 50 mm long. They are magnetized in the thickness direction and are of the= composition known as N38. They have a coercive force of about 12,000 Oerste= ds (CGS units), corresponding to 1.2 Teslas in the SI system.

  Construction of a four-pole magnet assembly is very simple, but also=20= very hazardous. These magnets are attracted to steel and to each other with=20= a force of about 57 pounds per square inch, and any skin caught between them= can be badly nipped. You must keep loose magnets very far away from steel o= r each other and wear heavy leather work gloves when handling them. The magn= ets are brittle, and will break if they crash together or with steel. The po= le plates are mild steel, thick enough to carry the flux of the magnetic cir= cuit. More on that later. One of the plates must have clearance holes for 3/= 16" bolts, one hole in each corner. The plates, for the above magnet dimensi= ons, should measure two inches by at least three inches.


       So just two of these magnets coul= d probably lift you right off the floor......
       You need to plan your assembly, place t= he magnets over a 3 ft away and be very careful. You will likely sometime ge= t a pinched finger, but with care you can avoid broken bones or a crushed fi= nger joint. I am not being alarmist.
       You MUST avoid flying magnets! &nb= sp; 

       Which is one reason why my designs favo= ur rather smaller magnets and separate the damping and detector functions. T= he other reason for this is that the systems were designed for school use an= d you then want to separate out the two functions for educational / demonstr= ation purposes. You already have a large field increase by using the NdFeB m= agnets in comparison with Alnico and a more sensitive and flexible orientati= on with the quad magnet arrangement, so you can cut down on total coil turns= and still get better performance. This can reduce the resistance and may al= low ~more signal amplification. The minimum noise is determined by the input= noise impedance characteristics of the opamp. You ~match the coil resistanc= e to this notional resistance figure to get the best performance. In amateur= seismic work, you are usually limited in practice by the ambient environmen= tal noise.

       I prefer zinc plated 1/4" OD set screws= to 3/16" OD. Mostly personal choice, but they are a bit more rigid and it a= lso increases the magnetic coupling between the two backing plates, which ca= n carry stray fields. You won't get the total flux of any two magnets matchi= ng exactly.

  Slide two magnets onto e= ach plate, with opposite poling on each plate. When you have one magnet in p= osition on a plate, carefully hold the second magnet above the first. You wi= ll feel either an attraction or a repulsion of the second magnet toward the=20= one on the plate. Make sure the force is repulsive, then slide the second ma= gnet into place beside the first. When the magnets are positioned on each pl= ate, make a wooden or plastic shim somewhat thinner than the final magnet ga= p you intend to use. I would use a shim about six inches long and the same w= idth as the paired magnets, which would be about 1.5 inches for the example.= With the shim covering the magnets of one plate, hold the second plate over= it, getting no closer than enough to determine if the force between them is= attractive or repulsive. The correct alignment is indicated by an attractiv= e force. You now place the upper plate (magnets down) on the shim at one end= of the lower plate and slide the upper plate and magnets up over the lower=20= magnets. You now have a sandwich of upper and lower assemblies tightly squee= zing the shim in between.


       If you are doing it this way, I suggest= that you attach the plastic shim or preferably a wood block firmly to the f= irst magnet with PVC or gaffer tape. This can help prevent accidents. The fo= rces can be really dangerous.

  Place four bolts in the=20= plate with the holes. Note than these bolts are used to hold the plates apar= t, not together. Use the bolts to jack the plates apart to get the desired g= ap spacing, and then you can withdraw the shim. If each of your plates have=20= clearance holes drilled in them, you will need two nuts for each screw.

       I mount the two magnets on the first bl= ock. Then I fit the four bolts with two nuts each. The inner one I do up fin= ger tight, the outer one I leave at ~ 1.5" along the thread. Then I prepare=20= the second plate. I grip the first plate with my hand to prevent the plates=20= getting too close and slide the second plate onto the bolts. With Bob's more= powerful magnets, I would use a wood safety block and adhesive tape in plac= e of my hand. I rock this plate till it contacts the nuts and then back off=20= the nuts sequentially about a turn at a time till I get the desired central=20= magnet separation.

  Now it is time to discus= s what field strength you get, and what thickness of steel is required. Supp= ose for my example using 6 mm thick magnets, I use a gap of 6 mm. The result= ing distance between plates is 18 mm, 12 mm filled with magnet, and 6 mm wit= h air. I call the ratio of total magnet thickness to total plate separation=20= the filling factor. To a first approximation, the gap field the coercive for= ce of the magnetic material multiplied by the filling factor. In this exampl= e, the coercive force is 12 KOe and the filling factor is 2/3, so the gap fi= eld is 8 KOe. The accuracy of this estimate depends on the magnet width comp= ared to the gap size. If the gap becomes appreciable compared to the width,=20= you will get more fringing field and less-than-expected gap field.

       Can you run through the maths and assum= ptions of this please?

   For my example mag= net structure, I use 1/4 inch thick steel plates. I find that there is a ver= y slight saturation of the plates in the region between magnet pairs. When I= use 24 mm wide magnets, there is a lot of saturation and a lot of external=20= stray field around the whole assembly. I have to put steel side plates on th= e assembly to eliminate the saturation and the stray field. Steel can carry=20= a flux density of about 20 to 24 KOe without saturation. Without saturation,= the magnetic circuit of a 4-pole structure consists of a closed rectangular= flux path, with lines traveling through magnets, gaps, and steel. The steel= must carry the same total number of lines of flux as the gap and magnets. T= he number of lines is proportional to the gap flux density multiplied by the= magnet width. In the example of 8 KOe and 18 mm width, this corresponds to=20= 8,000 times 1.8, or 14,000 lines per lineal centimeter of magnet structure.=20= The quarter-inch-thick steel (0.625 cm) must carry a flux density of 22,000=20= KOe. It does so, barely.


       Kaye and Laby list the flux density of=20= mild steel at 21.5 k Oer at saturation.
      If you made the backing plate to just cover t= he magnets, all the flux would have to go through the centre of the mild ste= el plate. If you increase the backing plate area, flux can go through this s= urrounding strip, reducing the overall thickness required, down to about 1/2= minimum, before you have to increase the thickness. I leave a 1/2" wide bor= der around my magnets.
       The closer the two plates, the greater=20= the field in the gap, so the more flux that the plates have to carry in the=20= critical central area. 
       I put a rounded corner of the magnet ju= st onto the backing plate, rotate it till one edge is on the plate, reduce t= he angle till maybe 1/4 of the magnet is flat on the plate and then slide th= e magnet into position.

  The next topic is coil d= esign. By following the above magnet assembly design principles, you know th= e approximate gap field, so by also knowing the magnet length you will be ab= le to estimate the number of coil turns you will need to achieve a given out= put sensitivity in volts per meter per second. If the end loops of the coil=20= extend beyond the ends of the magnet, each turn is immersed in a total field= length of twice the magnet length. In the example design, the magnet length= is 50 mm, so L per turn is 0.1 m.

  The output voltage generated by the moving coil is Volts =3D B * N *=20= L * Vel, where B is field strength in Teslas, N is number of turns, L is len= gth per turn in the field, and Vel is velocity in meters per second. One Tes= la corresponds to 10,000 Oersteds. Suppose n =3D 1100, B =3D 0.8 Tesla, and=20= L =3D 0.1 meter. Then Volts/Vel =3D 0.8 * 1100 * 0.1 =3D 88 v-s/m, which is=20= a good number to strive for.

  A wire size of #38 or less will allow this number of turns to fit com= fortably within the gap field cross-section. The coil will have a resistance= low enough to permit resistive shunt damping of a pendulum weighing up to a= kilogram, in my opinion. My sensors have a pendulum mass of about 0.1Kg, an= d critical damping is achieved at about 30 kOhms. Since the coil resistance=20= is only 340 Ohms, the shunt damping imposes negligible loss on output sensit= ivity. Even a kilogram mass would require only about 10% loss of output usin= g shunt damping.


       The damping force required also depends= on the set period. What period are you using?
       What effect does this damping current h= ave on the input noise in practice? Can it be significant?
       Looking at the commonly available lists= of insulated wire, the Beldsol polyurethane coated copper wire which you ca= n solder directly without stripping is stocked in sizes down to 36 AWG. You=20= may have to hunt hard / go to professional suppliers for 38 AWG and smaller=20= diameters - higher numbers. The properties of copper wire are listed in the=20= www under AWG copper wire.

  There is one significant= complication to this type of magnet and coil design, having to do with the=20= fact that pure copper is diamagnetic, and coil and its pendulum are subject=20= to forces other than the desired restoring force of a garden gate pendulum.=20= In the example design this diamagnetic force is a decentering force, making=20= it very difficult to adjust the sensor to a state of stable long period equi= librium. I reduce this effect by essentially potting the coil in acrylic pla= stic, which is also diamagnetic, and having the boundaries of the plastic ex= tend well outside the edges of the magnetic field. Using a heavier pendulum=20= would be of great benefit, as well.


       Pure copper is diamagnetic, but some co= pper wire contains a tiny amount of iron, which is strongly paramagnetic. Th= e properties may vary in practice. This is even more of a pest and can resul= t in the coil being attracted by the strong field gradient at the edge of th= e magnets. With these high fields, you can get the situation where the coil=20= has two stable positions over the edges of the magnets, with an unstable reg= ion in between. You may need to check your reel, or your wound coil, or wind= a sample coil for a repulsion / attraction test. You may get an even strong= er effect when the winding is close to / over the central N/S magnet join.        You can reduce this type of problem by=20= increasing the separation between the coil and the edges of the magnets a bi= t, but this reduces the sensitivity; by limiting the travel of the arm so th= at the coil does not get too close to the edges of the magnets and by increa= sing the magnet area and hence the available coil travel, but this may requi= re a thicker backing plate and gives a higher coil resistance. The force on=20= the winding is proportional to H x dH/dr, which falls off very rapidly with=20= increasing r at the edges of the magnet.
       I appreciate the value of using a wider= plastic plate to reduce the change of susceptibility with position. I suspe= ct that it may be important to have a solid plastic core to the coil to redu= ce forces associated with the cental magnet join.
       Also, the less copper that is used, the= lower the force.

       Regards,

       Chris Chapman Subject: Re: Sensor magnet and coil design From: Bobhelenmcclure@....... Date: Sat, 7 Oct 2006 01:11:01 EDT On Fri, 6 Oct 2006 06:18:14 EDT, ChrisAtUpw@....... writes: > Now it is time to discuss what field strength you get, and what thickness > of steel is required. Suppose for my example using 6 mm thick magnets, I use > a gap of 6 mm. The resulting distance between plates is 18 mm, 12 mm filled > with magnet, and 6 mm with air. I call the ratio of total magnet thickness to > total plate separation the filling factor. To a first approximation, the gap > field the coercive force of the magnetic material multiplied by the filling > factor. In this example, the coercive force is 12 KOe and the filling factor > is 2/3, so the gap field is 8 KOe. The accuracy of this estimate depends on > the magnet width compared to the gap size. If the gap becomes appreciable > compared to the width, you will get more fringing field and less-than-expected > gap field. Can you run through the maths and assumptions of this please? Hi Chris, I am assuming that the Nd magnet material is very hard magnetically, and has an incremental permeability almost the same as air. It can be considered to be an empty volume whose pole faces are coated uniformly with magnetic charges. Charges on one face are connected by lines of force to opposite charges. First consider a stack of magnets with infinitesimal gaps between them. In this case, opposite charges are adjacent, so all the lines cross the gap to the next magnet, and none travel back through the magnet to the opposing poles at the other end, and we get at the gap the flux of the short circuit coercive force. As we widen the gaps, more and more flux returns to the opposing face of each magnet instead of crossing the gap to the next magnet. With this line of reasoning, we are down to a flux of 50% when the gap spacing equals the magnet thickness, and so on. The four pole magnet structure can be shown to be similar in field pattern to a repeating structure of magnets and gaps, so my conclusions rest on the validity of the assumption of a relative permeability of 1.0 for the magnets. If the incremental permeability is higher than 1, then the field will fall off faster with increasing gap spacing. The finite transverse dimensions of the magnets is another reason for more rapid falloff. --Bob
On Fri, 6 Oct 2006 06:18:14 EDT, ChrisAtUpw@.......=20 writes:
>   Now it is time to discuss what field strength yo= u=20 get, and what thickness
> of steel is required. Suppose for my exampl= e=20 using 6 mm thick magnets, I use
> a gap of 6 mm. The resulting distan= ce=20 between plates is 18 mm, 12 mm filled
> with magnet, and 6 mm with ai= r. I=20 call the ratio of total magnet thickness to
> total plate separation=20= the=20 filling factor. To a first approximation, the gap
> field the coerciv= e=20 force of the magnetic material multiplied by the filling
> factor. In= =20 this example, the coercive force is 12 KOe and the filling factor
> i= s=20 2/3, so the gap field is 8 KOe. The accuracy of this estimate depends on=20
> the magnet width compared to the gap size. If the gap becomes=20 appreciable
> compared to the width, you will get more fringing field= and=20 less-than-expected
> gap field.
 
       Can you run through the maths and=20 assumptions of this please?

Hi Chris,

  I am assuming that the Nd magnet material is very hard=20 magnetically, and has an incremental permeability almost the same as air. It= can=20 be considered to be an empty volume whose pole faces are coated uniform= ly=20 with magnetic charges. Charges on one face are connected by lines of force t= o=20 opposite charges. First consider a stack of magnets with infinitesimal gaps=20 between them. In this case, opposite charges are adjacent, so all the lines=20 cross the gap to the next magnet, and none travel back through the magnet to= the=20 opposing poles at the other end, and we get at the gap the flux of the short= =20 circuit coercive force. As we widen the gaps, more and more flux returns to=20= the=20 opposing face of each magnet instead of crossing the gap to the next magnet.= =20 With this line of reasoning, we are down to a flux of 50% when the gap spaci= ng=20 equals the magnet thickness, and so on.
 
  The four pole magnet structure can be shown to be similar in fie= ld=20 pattern to a repeating structure of magnets and gaps, so my conclusions rest= on=20 the validity of the assumption of a relative permeability of 1.0 for the=20 magnets. If the incremental permeability is higher than 1, then the field wi= ll=20 fall off faster with increasing gap spacing. The finite transverse dimension= s of=20 the magnets is another reason for more rapid falloff.
 
--Bob
 Subject: Korean nuclar test From: Bob Barns royb1@........... Date: Sat, 07 Oct 2006 10:35:19 -0400 Hi gang, N. Korea may test a nuclear bomb. I realize that is a complicated question but maybe someone can give a rough estimate of how big a seismic signal might be produced. Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Korean nuclar test From: jimo17@........ Date: Sat, 7 Oct 2006 10:07:18 -0700 Hi Bob- John Louie at UNR has a wonderful explanation of the Richter Mag scale at: http://www.seismo.unr.edu/ftp/pub/louie/class/100/magnitude.html It plots Mag vs Yields (bombs & explosions) Jim On Sat, 07 Oct 2006 10:35:19 -0400 Bob Barns writes: > Hi gang, > N. Korea may test a nuclear bomb. I realize that is a complicated > > question but maybe someone can give a rough estimate of how big a > seismic signal might be produced. > Bob > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Korean nuclar test From: apsn apsn@........... Date: Sat, 07 Oct 2006 09:17:03 -0800 http://earthquake.usgs.gov/learning/faq.php?categoryID=2&faqID=33 Bob Hammond Public Seismic Network - Alaska http://apsn.awcable.com At 04:39 AM 10/7/2006, you wrote: >Hi gang, > N. Korea may test a nuclear bomb. I realize that is a complicated > question but maybe someone can give a rough estimate of how big a > seismic signal might be produced. >Bob > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with the body >of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Korean nuclar test From: apsn apsn@........... Date: Sat, 07 Oct 2006 09:31:33 -0800 Here's another link: http://en.wikipedia.org/wiki/Moment_magnitude_scale Bob Hammond Public Seismic Network - Alaska http://apsn.awcable.com At 04:39 AM 10/7/2006, you wrote: >Hi gang, > N. Korea may test a nuclear bomb. I realize that is a complicated > question but maybe someone can give a rough estimate of how big a > seismic signal might be produced. >Bob > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with the body >of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Seismometer for Central Illinois From: "Armstrong" joe.armstrong@............. Date: Sun, 8 Oct 2006 00:03:54 -0500 I live in a subdivision in a city in Central Illinois. The geological = survey tells my that in my area, that bedrock is 10-30' feet below. I = have a basement, but also two active kids. I am interested in having a = seismometer that would be capable of detecting New Madrid activity. So far my attempts have involved the construction of a 8" coil using #34 = wire on a 3' - 3" pvc form using a pendulum of 6 magnetron magents. = Coil: Resistance of ~7.1kohm. =20 After I also have 3 - 4.5hz geophones. My questions follow: 1) Can you think of a project that I use the on-hand coil and magnets or = the geophones? Or should I just start over with another project? 2) Basement: Is it a suitable location? I have been told that that = gravel under the basement disperses most of the vibration. Would the = activity of the kids affect the readings? Should the seimometer be = physically secured to the concrete? 3) Can a home brew seismometer be effective in Central Illinois? Thanks for taking the time Joe
I live in a subdivision in a city in = Central=20 Illinois. The geological survey tells my that in my area, that bedrock = is 10-30'=20 feet below. I have a basement, but also two active kids. I am interested = in=20 having a seismometer that would be capable of detecting New Madrid=20 activity.
 
So far my attempts have involved the = construction=20 of a 8" coil using #34 wire on a 3' - 3" pvc form using a pendulum of 6=20 magnetron magents. Coil: Resistance of ~7.1kohm.  =
After I also have 3 - 4.5hz=20 geophones.
 
My questions follow:
1) Can you think of a project that I = use the=20 on-hand coil and magnets or the geophones? Or should I just start over = with=20 another project?
2) Basement: Is it a suitable = location? I have=20 been told that that gravel under the basement disperses most=20 of the vibration. Would the activity of the kids affect the = readings?=20 Should the seimometer be physically secured to the = concrete?
3) Can a home brew seismometer  be = effective=20 in Central Illinois?
 
Thanks for taking the time
Joe
Subject: ebay auction From: Bob Barns royb1@........... Date: Sun, 08 Oct 2006 10:26:46 -0400 Hi gang, Teledyne Geotech timing system TG-120 Seismometer Item number: 140039611592 ends Oct 13 Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismometer for Central Illinois From: jonfr500@......... Date: Sun, 8 Oct 2006 15:02:03 +0000 Hi A 4.5Hz geophone would work fine for you. Your local noise pickup would be = a bit hig (depending on car traffic and other things). I use 4.5Hz geophone and it works great for me. See the plot here http://ea= rthquakes.jonfr.com Regards. J=F3n Fr=EDmann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismometer for Central Illinois From: "Thomas Dick" dickthomas01@............. Date: Sun, 8 Oct 2006 10:11:25 -0500 Hey Joe From Evansville, IN; I, too, have a basement. I sit on sediments much = deeper that yours. I have a 4 acre lake 25 ft from my back door. I have = a set of geophones outside and two lehmans and a homemade vertical in = the basement. It is just my wife and I at home. When the kids come back = for the holidays, detection is almost useless. I srongly suggest you put = your geophones in the ground outside. This will give you something to = compare house activities to. When things are quiet in the house, lehmans = will detect activity to your satisfaction well beyond the New Madrid = zone. Most New Madrid actiivty consists of earthquakes below two in = magnitude. I copy some of these quakes. This magnitude quake isn't as = satisfying (and probably will not interest you as you get more = operational/ get the bugs out of your system) as some of the regional = quakes in the 2.4 to 4 range. For instance, recently; the three quakes = in Maine, one in Oklahoma, the two in South Carolina were satisfying. = Plus, there is some quarry activity that you will see, and this activity = will hide/interfere with earthquake recording. When we are gone for a = week or so and the daughter-in-law or son come in to feed the cat, I can = tell the difference between her 120 lb walk in the hall upstairs to my = son's 210 lb walk. What I don't understand, is that the washing machine, = dryer and even the sump pump in the basement have not been a problem. = But you walk around down there! Or let the December sun fall the the = basement floor! There has been some very good discussions on the PSN = network in the last week or so. You will be wise and a penny saved to = heed them. Tom
Hey Joe
 
From Evansville, IN; I, too, have a = basement. I sit=20 on sediments much deeper that yours. I have a 4 acre lake 25 ft from my = back=20 door. I have a set of geophones outside and two lehmans and a homemade = vertical=20 in the basement. It is just my wife and I at home. When the kids come = back for=20 the holidays, detection is almost useless. I srongly suggest you put = your=20 geophones in the ground outside. This will give you something to = compare=20 house activities to. When things are quiet in the house, lehmans will = detect=20 activity to your satisfaction well beyond the New Madrid zone. Most = New=20 Madrid actiivty consists of earthquakes below two in magnitude. I copy = some of=20 these quakes. This magnitude quake isn't as satisfying (and probably = will not=20 interest you as you get more operational/ get the bugs out of your = system) as=20 some of the regional quakes in the 2.4 to 4 range. For instance, = recently; the=20 three quakes in Maine, one in Oklahoma, the two in South Carolina were=20 satisfying. Plus, there is some quarry activity that you will see, and = this=20 activity will hide/interfere with earthquake recording. When we are gone = for a=20 week or so and the daughter-in-law or son come in to feed the cat, I can = tell=20 the difference between her 120 lb walk in the hall upstairs to my son's = 210 lb=20 walk. What I don't understand, is that the washing machine, dryer and = even the=20 sump pump in the basement have not been a problem. But you walk around = down=20 there! Or let the December sun fall the the basement floor! There has = been some=20 very good discussions on the PSN network in the last week or so. You = will be=20 wise and a penny saved to heed them.
Tom
Subject: Re: Korean nuclar test From: "Connie and Jim Lehman" lehmancj@........... Date: Sun, 8 Oct 2006 12:57:41 -0400 Bob--Your interest in the Korean Nuclear Test is a nice challenge to consider. My only nuke tests copied here in VA years ago were the announced tests in Nevada----They were given a magnitude rating after the event (by the NEIS)--We probably received 10 to a dozen over 2 years -the mid l970's. Mag. 4 barely read--Mag. 5's much better, and several over 6.0 Mag--looked like a typical west coast/Calif. event in good detail. Travel time on the events was 6 minutes, 10 seconds for us The main signature difference was the obvious lack of a "S" wave, as the detonation was in a small spherical cavity a kilometer or two underground--and appeared as a point source. I understand some countries attempting tests during the banned times elongated their cavities to create a shear "S" componet in the signature.--and they appeared as a natural event. Perhaps this background note may be helpful. I am certain you will find more information on the web pages suggested. A Mag.5.5 or greater from Korea will be widely copied, no doubt by amateurs as well as professionals-- Have a good day-- Jim Lehman ----- Original Message ----- From: "Bob Barns" To: "psn mail" Sent: Saturday, October 07, 2006 10:35 AM Subject: Korean nuclar test > Hi gang, > N. Korea may test a nuclear bomb. I realize that is a complicated > question but maybe someone can give a rough estimate of how big a > seismic signal might be produced. > Bob > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismometer for Central Illinois From: ChrisAtUpw@....... Date: Sun, 8 Oct 2006 14:26:00 EDT In a message dated 2006/10/08, joe.armstrong@............. writes: > I live in a subdivision in a city in Central Illinois. The geological > survey tells my that in my area, that bedrock is 10-30' feet below. I have a > basement, but also two active kids. I am interested in having a seismometer that > would be capable of detecting New Madrid activity. > > So far my attempts have involved the construction of a 8" coil using #34 > wire on a 3' - 3" pvc form using a pendulum of 6 magnetron magents. Coil: > Resistance of ~7.1kohm. > After I also have 3 - 4.5hz geophones. Hi Joe, What are you calling 'Magnetron Magnets', please? What shape and size? Are they the donut type out of microwave cookers? Or the large horse shoe types, maybe up to 10" across the base from radar sets? See 3 & 4th photos from bottom at http://pages.prodigy.net/fxc/JC.html If you mount ANY magnets on the seismometer arm, you will likely find it very noisy. Seismometers may be capable of measuring movements down to a few 10s of nano metres. 1 thou of an inch = 25,400 nano metres. Magnets mounted on a seismometer arm are likely to pick up every large pulse on the house utility wiring, fridges turning on and off, washing machines, passing cars, trucks and trains, changes in the Earth's magnetic field...... This is definitely NOT a good idea. You should plan on putting the coil on the arm and on using a non magnetic mass. Brass is easy to machine. Lead and copper are also OK. If you use a horizontal copper plate(s) for the mass, you can damp it directly with magnets. I suggest that you stay clear of oil damping. It is temperature sensitive, relatively difficult to set up correctly and tends to be messy. My questions follow: > 1) Can you think of a project that I use the on-hand coil and magnets or > the geophones? Or should I just start over with another project? The coil is rather too large for ease of use. You may be able to buy 'spare coils' for sequence timers used on washing machines? The size depends on the dimension of the magnet poles and the layout. You usually use a hollow section / ring coil of about the same diameter. You might want to consider using NdFeB magnets? They give a much higher output and are 'affordable'. I use 1" square Neos in a quad arrangement with a rectangular coil about 1.25" long by 3/4" wide internal and 2,500 turns of finer wire. Resistance about 500 Ohm. See http://jclahr.com/science/psn/chapman/lehman/index.html Are the geophones the 4.5 Hz triaxial plastic cased ones that Larry sells? If so, I suggest that you get the geophones 'up and runnning' first to 'get some experience'. Larry at http://psn.quake.net/ sells amplifiers and an ADC for seismic work. Maybe try the geophones out at various locations to find out what other local and surface signals there are? > 2) Basement: Is it a suitable location? I have been told that that gravel > under the basement disperses most of the vibration. Would the activity of the > kids affect the readings? Should the seimometer be physically secured to the > concrete? The basement would likely be the best place to start with. Does it have a concrete floor? Alternatively, can you provide a shed or some protection in the garden, away from the house or nearby tall trees? You will likely find that the seismic signals will get through the gravel quite OK. You don't say anything about your kid's size, weight or activities! Your geophones should sit on concrete OK, but for long term use you should consider siting them maybe 20 ft or more from the house and underground, maybe 2 to 3 ft deep in a waterproof container? There is a lot of 'surface noise' about, which you probably don't want to see. If you are mounting a Lehman type seismometer on concrete, it is a good idea to provide three glazed tiles / glass squares / metal plates glued to the concrete with pool adhesive or similar to provde a hard even surface for the levelling screws. I use 2" squares of 1/8" stainless steel. You may be able to reduce local / house noise a lot by low pass filtering down to 5 or 3 Hz. How far down is the water table? I was wondering if you could cut a hole in the basement floor and cast a separate concrete pillar directly into the gravel underneath? This could 'isolate you' to some extent from the activities in the house. Try using the existing floor first though, away from outside walls or any support pillars. > 3) Can a home brew seismometer be effective in Central Illinois? I can see absolutely no reason why not!! But do expect to see local environmental and house associated noise. You need to train yourself to recognise what earthquake signals look like and to identify other noise types and patterns. You will likely see quite a few local quakes which do not get reported on a WW information database, but which may or may not get reported on USGS. You may also see blasts from quarrying. Regards, Chris Chapman In a me= ssage dated 2006/10/08, joe.armstrong@............. writes:

I live in a subdivision in a ci= ty in Central Illinois. The geological survey tells my that in my area, that= bedrock is 10-30' feet below. I have a basement, but also two active kids.=20= I am interested in having a seismometer that would be capable of detecting N= ew Madrid activity.

So far my attempts have involved the construction of a 8" coil using #34 wir= e on a 3' - 3" pvc form using a pendulum of 6 magnetron magents. Coil: Resis= tance of ~7.1kohm. 
After I also have 3 - 4.5hz geophones.


Hi Joe,

       What are you calling 'Magnetron Magnets= ', please? What shape and size? Are they the donut type out of microwave coo= kers? Or the large horse shoe types, maybe up to 10" across the base from ra= dar sets? See 3 & 4th  photos from bottom at http://pages.prodigy.n= et/fxc/JC.html

       If you mount ANY magnets on the seismom= eter arm, you will likely find it very noisy. Seismometers may be cap= able of measuring movements down to a few 10s of nano metres. 1 thou of an i= nch =3D 25,400 nano metres.
       Magnets mounted on a seismometer arm ar= e likely to pick up every large pulse on the house utility wiring, fridges t= urning on and off, washing machines, passing cars, trucks and trains, change= s in the Earth's magnetic field...... This is definitely NOT a good idea.
       You should plan on putting the coil on=20= the arm and on using a non magnetic mass. Brass is easy to machine. Lead and= copper are also OK. If you use a horizontal copper plate(s) for the mass, y= ou can damp it directly with magnets.
       I suggest that you stay clear of oil da= mping. It is temperature sensitive, relatively difficult to set up correctly= and tends to be messy.

My questions follow:
1) Can you think of a project=20= that I use the on-hand coil and magnets or the geophones? Or should I just s= tart over with another project?


           The coil is rat= her too large for ease of use. You may be able to buy 'spare coils' for sequ= ence timers used on washing machines?
    The size depends on the dimension of the magnet poles and= the layout. You usually use a hollow section  / ring coil of about the= same diameter.

    You might want to consider using NdFeB magnets? They give= a much higher output and are 'affordable'.
    I use 1" square Neos in a quad arrangement with a rectang= ular coil about 1.25" long by 3/4" wide internal and 2,500 turns of finer wi= re. Resistance about 500 Ohm.
     See http://jclahr.com/science/psn/chapman/lehman/in= dex.html

    Are the geophones the 4.5 Hz triaxial plastic cased ones=20= that Larry sells?

       If so, I suggest that you get the geoph= ones 'up and runnning' first to 'get some experience'. Larry at http://psn.q= uake.net/ sells amplifiers and an ADC for seismic work. Maybe try the geopho= nes out at various locations to find out what other local and surface signal= s there are?

2) Basement: Is it a suitable l= ocation? I have been told that that gravel under the basement disperses most= of the vibration. Would the activity of the kids affect the readings? Shoul= d the seimometer be physically secured to the concrete?


       The basement would likely be the best p= lace to start with. Does it have a concrete floor?
       Alternatively, can you provide a shed o= r some protection in the garden, away from the house or nearby tall trees?        You will likely find that the seismic s= ignals will get through the gravel quite OK.

       You don't say anything about your kid's= size, weight or activities!

       Your geophones should sit on concrete O= K, but for long term use you should consider siting them maybe 20 ft or more= from the house and underground, maybe 2 to 3 ft deep in a waterproof contai= ner? There is a lot of 'surface noise' about, which you probably don't want=20= to see.

       If you are mounting a Lehman type seism= ometer on concrete, it is a good idea to provide three glazed tiles / glass=20= squares / metal plates glued to the concrete with pool adhesive or similar t= o provde a hard even surface for the levelling screws. I use 2" squares of 1= /8" stainless steel.
       You may be able to reduce local / house= noise a lot by low pass filtering down to 5 or 3 Hz.

       How far down is the water table? I was=20= wondering if you could cut a hole in the basement floor and cast a separate=20= concrete pillar directly into the gravel underneath? This could 'isolate you= ' to some extent from the activities in the house. Try using the existing fl= oor first though, away from outside walls or any support pillars. 

3) Can a home brew seismometer=20= be effective in Central Illinois?


       I can see absolutely no reason why not!= !
       But do expect to see local environmenta= l and house associated noise. You need to train yourself to recognise what e= arthquake signals look like and to identify other noise types and patterns.<= BR>        You will likely see quite a few local q= uakes which do not get reported on a WW information database, but which may=20= or may not get reported on USGS. You may also see blasts from quarrying.
       Regards,

       Chris Chapman Subject: Re: Shunt damping From: ChrisAtUpw@....... Date: Sun, 8 Oct 2006 20:13:09 EDT In a message dated 2006/10/08, Bobhelenmcclure writes: > > A wire size of #38 or less will allow this number of turns to fit > > comfortably within the gap field cross-section. The coil will have a > resistance low > > enough to permit resistive shunt damping of a pendulum weighing up to a > > kilogram, in my opinion. My sensors have a pendulum mass of about 0.1Kg, > and > > critical damping is achieved at about 30 kOhms. Since the coil resistance > is only > > 340 Ohms, the shunt damping imposes negligible loss on output sensitivity. > > > Even a kilogram mass would require only about 10% loss of output using > shunt > > damping. > > The damping force required also depends on the set period. What > period are you using? > What effect does this damping current have on the input noise in > practice? Can it be significant? > > Hi Chris, > I bought cheap low temperature enameled magnet wire from Alltronics. I > have both #38 (3.97 thou OD) and #40 gauge (3.14 thou OD). I never tried to > use the #40 wire, as it is difficult for me to see, let alone handle. I strip > by burning off the enamel. My friend Victor frowns on that, and recommends > fine emery paper. Hi Bob, Magnet wire is available from Alltronics in 1/4 lb reels, but it is Kynar insulated http://www.alltronics.com/cgi-bin/category.cgi?&category=MW&start=0 If you buy the polyurethane insulated wire like Beldsol, you don't have to strip it. If you put a hot iron and solder on it, the insulation just melts - no problems - but I have only found this wire down to 36 AWG - 5 thou OD. With the Kynar insulated wire, you have to strip it first before you can solder it. I usually use the edge of a wax candle flame (or a match) to first burn off this insulation. (You have to be very careful with a butane lighter not to melt the wire) Then I pull it fairly gently several times through two small pads of the very fine wire wool. This both cleans it effectively and hardens it a bit. I once only wound two coils with 40,000 turns of 44 AWG copper wire with 1 thou paper interleaving to measure paramagnetic susceptability - it took me two whole days.... > My horizontal sensors are easily shunt damped. On one of them set to 12 > second period, I measured a Q of 1.1 with a shunt resistance (including the > amplifier) of 66 kOhms. My formula for Q is Q = K * R / P. The value for K is > therefore 0.2. The mass of the coil and solder weight is about 100 grams. The > coil resistance is 340 Ohms, the number of turns is 1100, the field strength > is ~0.8T, the field length per turn is 0.1m, and the sensor output is 85 > v-s/m. If you know your own sensor's output, pendulum mass, and period, you can > work out your own value for K from the above information, and determine what > shunt damping resistance you would need. However, remember that the coil > resistance, in series with the shunt resistance (in parallel with the amplifier > input resistance) is the damping resistance. What is P please? > Volts= B*L*(dx/dt) > Force=B*L*I > I= Volts/R = B*L*(dx/dt)/R > Force= B*L*B*L*(dx/dt)/R > Force / (dx/dt)= (B*L)^2 / R > > I have not checked yet to see if the above equation is consistent with my > observed damping versus resistance. In the force equation, isn't the force proportional to the number of turns, whereas the inductance is proportional to the square of the number of turns and depends on the magnetic return path? How does the length of the pendulum, the set period and the mass factor into these equations, please? > Shunt damping makes it easy for me to check my sensors. I measure their > natural period by disconnecting the shunt, and discharging a small capacitor > across the sensor-amplifier terminals. The decay of oscillation amplitude > lets me make sure that the partially undamped oscillation has the expected Q > value, and the time between zero crossings gives me the natural period. I would > abandon the sport of seismometry if I could not control damping this way. I prefer to have my damping and sensors on separate fittings and their setup independant, but I can see the attraction of variable resistive damping if you choose very powerful sensor magnets and a low to moderate seismic mass. I tend to use rather smaller / thinner magnets for sensing and they do not have a serious diamagnetic repulsion problem, although I have observed this type of effect. I use wide Cu plate for the damping, so that the arm hits the side stops before the outer edge of the damping plate gets close to the outside edge of a magnet. I try to 'design out' problems when possible. If you are using feedback sensors with electronically extended periods, Cu plate damping is a lot quieter than velocity feedback from a differentiated position signal. Have you any comparisons of the input noise due to shunt damping vs plate damping - or the noise when undamped and when damped? Won't the induced current generate additional noise directly? Regards, Chris Chapman In a me= ssage dated 2006/10/08, Bobhelenmcclure writes:

>   A wire size of= #38 or less will allow this number of turns to fit
> comfortably within the gap field cross-section. The coil will have a re= sistance low
> enough to permit resistive shunt damping of a pendulum weighing up to a=
> kilogram, in my opinion. My sensors have a pendulum mass of about 0.1Kg= , and
> critical damping is achieved at about 30 kOhms. Since the coil resistan= ce is only
> 340 Ohms, the shunt damping imposes negligible loss on output sensitivi= ty.
> Even a kilogram mass would require only about 10% loss of output using=20= shunt
> damping.

       The damping force required also depend= s on the set period. What period are you using?
       What effect does this damping current h= ave on the input noise in practice? Can it be significant?

Hi Chris,
    I bought cheap low temperature enameled magnet wire from=20= Alltronics. I have both #38 (3.97 thou OD) and #40 gauge (3.14 thou OD). I n= ever tried to use the #40 wire, as it is difficult for me to see, let alone=20= handle. I strip by burning off the enamel. My friend Victor frowns on that,=20= and recommends fine emery paper.


Hi Bob,

    Magnet wire is available from Alltronics in 1/4 lb reels,= but it is Kynar insulated
       http://www.alltronics.com/cgi-bin/categ= ory.cgi?&category=3DMW&start=3D0

       If you buy the polyurethane insulated w= ire like Beldsol, you don't have to strip it. If you put a hot iron and sold= er on it, the insulation just melts - no problems - but I have only found th= is wire down to 36 AWG - 5 thou OD.

       With the Kynar insulated wire, you have= to strip it first before you can solder it. I usually use the edge of a wax= candle flame (or a match) to first burn off this insulation. (You have to b= e very careful with a butane lighter not to melt the wire) Then I pull it fa= irly gently several times through two small pads of the very fine wire wool.= This both cleans it effectively and hardens it a bit.

       I once only wound two coils with 40,000= turns of 44 AWG copper wire with 1 thou paper interleaving to measure param= agnetic susceptability - it took me two whole days....

  My horizontal sensors ar= e easily shunt damped. On one of them set to 12 second period, I measured a=20= Q of 1.1 with a shunt resistance (including the amplifier) of 66 kOhms. My f= ormula for Q is Q =3D K * R / P. The value for K is therefore 0.2. The mass=20= of the coil and solder weight is about 100 grams. The coil resistance is 340= Ohms, the number of turns is 1100, the field strength is ~0.8T, the field l= ength per turn is 0.1m, and the sensor output is 85 v-s/m. If you know your=20= own sensor's output, pendulum mass, and period, you can work out your own va= lue for K from the above information, and determine what shunt damping resis= tance you would need. However, remember that the coil resistance, in series=20= with the shunt resistance (in parallel with the amplifier input resistance)=20= is the damping resistance.


       What is P please?

Volts=3D B*L*(dx/dt)
Force=3DB*L*I
I=3D Volts/R =3D B*L*(dx/dt)/R
Force=3D B*L*B*L*(dx/dt)/R
Force / (dx/dt)=3D (B*L)^2 / R

  I have not checked yet to see if the above equation is consist= ent with my observed damping versus resistance.


    In the force equation, isn't the force proportional to th= e number of turns, whereas the inductance is proportional to the square of t= he number of turns and depends on the magnetic return path?

       How does the length of the pendulum, th= e set period and the mass factor into these equations, please?

   Shunt damping make= s it easy for me to check my sensors. I measure their natural period by disc= onnecting the shunt, and discharging a small capacitor across the sensor-amp= lifier terminals. The decay of oscillation amplitude lets me make sure that=20= the partially undamped oscillation has the expected Q value, and the time be= tween zero crossings gives me the natural period. I would abandon the sport=20= of seismometry if I could not control damping this way.


       I prefer to have my damping and sensors= on separate fittings and their setup independant, but I can see the attract= ion of variable resistive damping if you choose very powerful sensor magnets= and a low to moderate seismic mass.

       I tend to use rather smaller / thinner=20= magnets for sensing and they do not have a serious diamagnetic repulsion pro= blem, although I have observed this type of effect.
       I use wide Cu plate for the damping, so= that the arm hits the side stops before the outer edge of the damping plate= gets close to the outside edge of a magnet. I try to 'design out' problems=20= when possible.

       If you are using feedback sensors with=20= electronically extended periods, Cu plate damping is a lot quieter than velo= city feedback from a differentiated position signal.
  
      Have you any comparisons of the input noise d= ue to shunt damping vs plate damping - or the noise when undamped and when d= amped? Won't the induced current generate additional noise directly?  <= BR>
       Regards,

       Chris Chapman Subject: Re: Korean nuclar test From: Canie canie@........... Date: Sun, 08 Oct 2006 22:00:01 -0700 It appears they have done the test -  (about 9:50pm 10/08/06 - PDT)
http://news.yahoo.com/s/ap/20061009/ap_on_re_as/koreas_nuclear_102

An official at South Korea's seismic monitoring center confirmed a magnitude-3.6 tremor felt at the time North Korea said it conducted the test was not a natural occurrence.

Australia also said there was seismic confirmation that North Korea conducted a nuclear test.

Canie

At 09:57 AM 10/8/2006, you wrote:
Bob--Your interest in the Korean Nuclear Test is a nice challenge to
consider.  My only nuke tests copied here in VA years ago were the announced
tests in Nevada----They were given a magnitude rating after the event (by
the NEIS)--We probably received 10 to a dozen over 2 years -the mid l970's.
Mag. 4 barely read--Mag. 5's much better, and several over 6.0 Mag--looked
like a typical west coast/Calif. event in good detail.   Travel time on the
events was 6 minutes, 10 seconds for us The main signature difference was
the obvious lack of a "S" wave, as the detonation was in a small spherical
cavity a kilometer or two underground--and appeared as a point source.
    I understand some countries attempting tests during the banned times
elongated their cavities to create a shear "S" componet in the
signature.--and they appeared as a natural event.
  Perhaps this background note may be helpful.  I am certain you will find
more information on the web pages suggested.  A Mag.5.5 or greater from
Korea will be widely copied, no doubt by amateurs as well as professionals--
   Have a good day-- Jim Lehman
Subject: Re: Korean nuclar test From: apsn apsn@........... Date: Sun, 08 Oct 2006 21:11:08 -0800 http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/ustqab.php At 09:00 PM 10/8/2006, you wrote: >It appears they have done the test - (about 9:50pm 10/08/06 - PDT) >http://news.yahoo.com/s/ap/20061009/ap_on_re_as/koreas_nuclear_102 > >An official at >South >Korea's seismic monitoring center confirmed a magnitude-3.6 tremor >felt at the time North Korea said it conducted the test was not a >natural occurrence. > >Australia also said there was seismic confirmation that North Korea >conducted a nuclear test. > >Canie > >At 09:57 AM 10/8/2006, you wrote: >>Bob--Your interest in the Korean Nuclear Test is a nice challenge to >>consider. My only nuke tests copied here in VA years ago were the announced >>tests in Nevada----They were given a magnitude rating after the event (by >>the NEIS)--We probably received 10 to a dozen over 2 years -the mid l970's. >>Mag. 4 barely read--Mag. 5's much better, and several over 6.0 Mag--looked >>like a typical west coast/Calif. event in good detail. Travel time on the >>events was 6 minutes, 10 seconds for us The main signature difference was >>the obvious lack of a "S" wave, as the detonation was in a small spherical >>cavity a kilometer or two underground--and appeared as a point source. >> I understand some countries attempting tests during the banned times >>elongated their cavities to create a shear "S" componet in the >>signature.--and they appeared as a natural event. >> Perhaps this background note may be helpful. I am certain you will find >>more information on the web pages suggested. A Mag.5.5 or greater from >>Korea will be widely copied, no doubt by amateurs as well as professionals-- >> Have a good day-- Jim Lehman > >Bob Hammond >Public Seismic Network - Alaska >http://apsn.awcable.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Korean nuclar test From: Dave Nelson davenn@............... Date: Mon, 09 Oct 2006 15:57:12 +1000 well it looks like they have done the test and it registered a M4.2 on the NEIC listing cheers Dave > > Hi gang, > > N. Korea may test a nuclear bomb. I realize that is a complicated > > question but maybe someone can give a rough estimate of how big a > > seismic signal might be produced. > > Bob > > > > __________________________________________________________ > > > > Public Seismic Network Mailing List (PSN-L) > > > > To leave this list email PSN-L-REQUEST@.............. with > > the body of the message (first line only): unsubscribe > > See http://www.seismicnet.com/maillist.html for more information. > > > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. > > > >-- >No virus found in this incoming message. >Checked by AVG Free Edition. >Version: 7.1.407 / Virus Database: 268.13.1/466 - Release Date: 7/10/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.407 / Virus Database: 268.13.1/466 - Release Date: 7/10/2006 __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Korean nuclar test From: jonfr500@......... Date: Mon, 9 Oct 2006 09:19:18 +0000 Hi Did anyone here register this test ? Regards. J=F3n Fr=EDmann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Shunt damping From: "Geoffrey" gmvoeth@........... Date: Mon, 9 Oct 2006 07:36:59 -0700 What is the possibility of using one turn of a heavy guage wire as a single loop and sharpening the ends to a point then sensing the voltages at the points I would think that changing the cross sectional area would increase the voltages by concentrating electrons or if you are faster in your thought holes sort of like having a resistor in the middle but no power loss. This is the way you change impedances in antennas or so i understand and what is a velocity sensor but an odd kind of antenna. ----- Original Message ----- From: To: Sent: Sunday, October 08, 2006 5:13 PM Subject: Re: Shunt damping > In a message dated 2006/10/08, Bobhelenmcclure writes: > >> > A wire size of #38 or less will allow this number of turns to fit >> > comfortably within the gap field cross-section. The coil will have a >> resistance low >> > enough to permit resistive shunt damping of a pendulum weighing up to a >> > kilogram, in my opinion. My sensors have a pendulum mass of about 0.1Kg, >> and >> > critical damping is achieved at about 30 kOhms. Since the coil resistance >> is only >> > 340 Ohms, the shunt damping imposes negligible loss on output sensitivity. >> >> > Even a kilogram mass would require only about 10% loss of output using >> shunt >> > damping. >> >> The damping force required also depends on the set period. What >> period are you using? >> What effect does this damping current have on the input noise in >> practice? Can it be significant? >> >> Hi Chris, >> I bought cheap low temperature enameled magnet wire from Alltronics. I >> have both #38 (3.97 thou OD) and #40 gauge (3.14 thou OD). I never tried to >> use the #40 wire, as it is difficult for me to see, let alone handle. I strip >> by burning off the enamel. My friend Victor frowns on that, and recommends >> fine emery paper. > > Hi Bob, > > Magnet wire is available from Alltronics in 1/4 lb reels, but it is Kynar > insulated > http://www.alltronics.com/cgi-bin/category.cgi?&category=MW&start=0 > > If you buy the polyurethane insulated wire like Beldsol, you don't > have to strip it. If you put a hot iron and solder on it, the insulation just > melts - no problems - but I have only found this wire down to 36 AWG - 5 thou OD. > > With the Kynar insulated wire, you have to strip it first before you > can solder it. I usually use the edge of a wax candle flame (or a match) to > first burn off this insulation. (You have to be very careful with a butane > lighter not to melt the wire) Then I pull it fairly gently several times through two > small pads of the very fine wire wool. This both cleans it effectively and > hardens it a bit. > > I once only wound two coils with 40,000 turns of 44 AWG copper wire > with 1 thou paper interleaving to measure paramagnetic susceptability - it took > me two whole days.... > >> My horizontal sensors are easily shunt damped. On one of them set to 12 >> second period, I measured a Q of 1.1 with a shunt resistance (including the >> amplifier) of 66 kOhms. My formula for Q is Q = K * R / P. The value for K is >> therefore 0.2. The mass of the coil and solder weight is about 100 grams. The >> coil resistance is 340 Ohms, the number of turns is 1100, the field strength >> is ~0.8T, the field length per turn is 0.1m, and the sensor output is 85 >> v-s/m. If you know your own sensor's output, pendulum mass, and period, you can >> work out your own value for K from the above information, and determine what >> shunt damping resistance you would need. However, remember that the coil >> resistance, in series with the shunt resistance (in parallel with the amplifier >> input resistance) is the damping resistance. > > What is P please? > >> Volts= B*L*(dx/dt) >> Force=B*L*I >> I= Volts/R = B*L*(dx/dt)/R >> Force= B*L*B*L*(dx/dt)/R >> Force / (dx/dt)= (B*L)^2 / R >> >> I have not checked yet to see if the above equation is consistent with my >> observed damping versus resistance. > > In the force equation, isn't the force proportional to the number of > turns, whereas the inductance is proportional to the square of the number of turns > and depends on the magnetic return path? > > How does the length of the pendulum, the set period and the mass > factor into these equations, please? > >> Shunt damping makes it easy for me to check my sensors. I measure their >> natural period by disconnecting the shunt, and discharging a small capacitor >> across the sensor-amplifier terminals. The decay of oscillation amplitude >> lets me make sure that the partially undamped oscillation has the expected Q >> value, and the time between zero crossings gives me the natural period. I would >> abandon the sport of seismometry if I could not control damping this way. > > I prefer to have my damping and sensors on separate fittings and their > setup independant, but I can see the attraction of variable resistive damping > if you choose very powerful sensor magnets and a low to moderate seismic > mass. > > I tend to use rather smaller / thinner magnets for sensing and they do > not have a serious diamagnetic repulsion problem, although I have observed > this type of effect. > I use wide Cu plate for the damping, so that the arm hits the side > stops before the outer edge of the damping plate gets close to the outside edge > of a magnet. I try to 'design out' problems when possible. > > If you are using feedback sensors with electronically extended > periods, Cu plate damping is a lot quieter than velocity feedback from a > differentiated position signal. > > Have you any comparisons of the input noise due to shunt damping vs > plate damping - or the noise when undamped and when damped? Won't the induced > current generate additional noise directly? > > Regards, > > Chris Chapman > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Shunt damping From: ChrisAtUpw@....... Date: Mon, 9 Oct 2006 10:48:08 EDT In a message dated 2006/10/09, gmvoeth@........... writes: > What is the possibility of using one turn of a heavy guage wire as a single > loop > and sharpening the ends to a point then sensing the voltages at the points > I would think that changing the cross sectional area would increase the > voltages by concentrating electrons or if you are faster in your thought holes > sort of like having a resistor in the middle but no power loss. Hi Geoff, Sorry, but you can't apply HF antenna theory to ~DC variations. You might be able to find the correct wire diameter for a single turn to provide critical damping. Regards, Chris Chapman In a me= ssage dated 2006/10/09, gmvoeth@........... writes:

What is the possibility of usin= g one turn of a heavy guage wire as a single loop
and sharpening the ends to a point then sensing the voltages at the points I would think that changing the cross sectional area would increase the volt= ages by concentrating electrons or if you are faster in your thought holes s= ort of like having a resistor in the middle but no power loss.
<= BR>
Hi Geoff,

       Sorry, but you can't apply HF antenna t= heory to ~DC variations.
       You might be able to find the correct w= ire diameter for a single turn to provide critical damping.

       Regards,

       Chris  Chapman Subject: Re: Seismometer for Central Illinois From: "Peter Laplante" laplantep@............... Date: Mon, 9 Oct 2006 08:54:34 -0700 Good morning Joe: I am just getting started with my equipment and do not have any = experience. I am afraid that I can not be of much help. I am using parts that I purchased from Larry Cockrine and hope to get my = station up and running in the next 6 months. Peter ----- Original Message -----=20 From: Armstrong=20 To: psn-l@................. Sent: Saturday, October 07, 2006 10:03 PM Subject: Seismometer for Central Illinois I live in a subdivision in a city in Central Illinois. The geological = survey tells my that in my area, that bedrock is 10-30' feet below. I = have a basement, but also two active kids. I am interested in having a = seismometer that would be capable of detecting New Madrid activity. So far my attempts have involved the construction of a 8" coil using = #34 wire on a 3' - 3" pvc form using a pendulum of 6 magnetron magents. = Coil: Resistance of ~7.1kohm. =20 After I also have 3 - 4.5hz geophones. My questions follow: 1) Can you think of a project that I use the on-hand coil and magnets = or the geophones? Or should I just start over with another project? 2) Basement: Is it a suitable location? I have been told that that = gravel under the basement disperses most of the vibration. Would the = activity of the kids affect the readings? Should the seimometer be = physically secured to the concrete? 3) Can a home brew seismometer be effective in Central Illinois? Thanks for taking the time Joe
Good morning Joe:
 
I am just getting started with my = equipment and do=20 not have any experience.  I am afraid that I can not be of much=20 help.
 
I am using parts that I purchased from = Larry=20 Cockrine and hope to get my station up and running in the next 6=20 months.
 
Peter
 
----- Original Message -----
From:=20 Armstrong
Sent: Saturday, October 07, = 2006 10:03=20 PM
Subject: Seismometer for = Central=20 Illinois

I live in a subdivision in a city in = Central=20 Illinois. The geological survey tells my that in my area, that bedrock = is=20 10-30' feet below. I have a basement, but also two active kids. I am=20 interested in having a seismometer that would be capable of detecting = New=20 Madrid activity.
 
So far my attempts have involved the = construction=20 of a 8" coil using #34 wire on a 3' - 3" pvc form using a pendulum of = 6=20 magnetron magents. Coil: Resistance of ~7.1kohm.  =
After I also have 3 - 4.5hz=20 geophones.
 
My questions follow:
1) Can you think of a project that I = use the=20 on-hand coil and magnets or the geophones? Or should I just start over = with=20 another project?
2) Basement: Is it a suitable = location? I=20 have been told that that gravel under the basement disperses most = of the vibration. Would the activity of the kids affect the=20 readings? Should the seimometer be physically secured to the=20 concrete?
3) Can a home brew seismometer =  be effective=20 in Central Illinois?
 
Thanks for taking the = time
Joe
Subject: RE: Korean nuclar test From: "Bob Hancock" carpediem1@......... Date: Mon, 9 Oct 2006 09:29:14 -0700 According to the news, the US has not confirmed that a nuclear device was exploded, only that the event was equivalent to a large amount of TNT, but below the kilo-ton level, a normal measurement for nuclear explosions. Does anyone in the PSN group have any thoughts about the different in seismic signatures between a chemical and nuclear explosion. I am wondering about the buildup of pressure that would generate the initial P-wave, and any differences in P-wave form that would be present between the chemical and nuclear explosions. Also, how does the rate of expansion on the shock wave compare between chemical and nuclear explosions. Bob Hancock __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Korean nuclar test From: apsn apsn@........... Date: Mon, 09 Oct 2006 08:58:43 -0800 Bob, how interesting that the very same question was a hot topic of debate in our house last night. Did the DPRK really set off a nuke or did they just set off a chemical explosion to fool everyone? I don't believe any but the closest seismometers would be able to discriminate between a nuke or a chemical explosion of M 4.2. The rise time of a nuke versus a chemical explosion would be different but to discriminate between the two at any distance from the hypocenter might be difficult. The modification of the initial P-wave by the country rock might make it even harder. This is something the CTBTO and USAF AFTAC and nuke-watching network operators WOULD know. :) Bob Hammond Public Seismic Network - Alaska http://apsn.awcable.com At 07:36 AM 10/9/2006, you wrote: >According to the news, the US has not confirmed that a nuclear device was >exploded, only that the event was equivalent to a large amount of TNT, but >below the kilo-ton level, a normal measurement for nuclear explosions. > >Does anyone in the PSN group have any thoughts about the different in >seismic signatures between a chemical and nuclear explosion. I am wondering >about the buildup of pressure that would generate the initial P-wave, and >any differences in P-wave form that would be present between the chemical >and nuclear explosions. Also, how does the rate of expansion on the shock >wave compare between chemical and nuclear explosions. > >Bob Hancock > > > > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. Bob Hammond Public Seismic Network - Alaska http://apsn.awcable.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Korean nuclar test From: jonfr500@......... Date: Mon, 9 Oct 2006 19:54:28 +0000 Hi Here is a explanation from BBC News about this test. http://news.bbc.co.uk/= 2/hi/asia-pacific/6033893.stm Regards. J=F3n Fr=EDmann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Korean nuclar test From: jonfr500@......... Date: Mon, 9 Oct 2006 20:11:03 +0000 Hi I found a picture of the wave from the explosion in North Korea. It can be = found here, http://www.nordlys.no/nyheter/article2339116.ece The news is in norsk. Regards. J=F3n Fr=EDmann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Korean nuclar test From: apsn apsn@........... Date: Mon, 09 Oct 2006 15:01:27 -0800 Hi all, Here's a great article on nuke detection and discrimination: http://www.ldeo.columbia.edu/res/pi/Monitoring/Doc/Srr_2005/PAPERS/03-22.pdf I went to graduate school with one of the authors (Dodge). Bob Hammond Public Seismic Network - Alaska http://apsn.awcable.com At 07:36 AM 10/9/2006, you wrote: >According to the news, the US has not confirmed that a nuclear device was >exploded, only that the event was equivalent to a large amount of TNT, but >below the kilo-ton level, a normal measurement for nuclear explosions. > >Does anyone in the PSN group have any thoughts about the different in >seismic signatures between a chemical and nuclear explosion. I am wondering >about the buildup of pressure that would generate the initial P-wave, and >any differences in P-wave form that would be present between the chemical >and nuclear explosions. Also, how does the rate of expansion on the shock >wave compare between chemical and nuclear explosions. > >Bob Hancock > > > > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. Bob Hammond Public Seismic Network - Alaska http://apsn.awcable.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Shunt damping From: Bobhelenmcclure@....... Date: Mon, 9 Oct 2006 21:17:07 EDT Hi Chris, For a damped pendulum, we are dealing with the equation F = m(d2x/dt2) + c(dx/dt) + kx, where F is some forcing function. m is mass, k is stiffness, and c is drag. Feynman defines k=m*Omega0^2, c=m*Gamma, and Q=Omega0/Gamma, where Omega0 is the natural frequency. In order to calculate the effect of a shunt load on the pickup coil for damping, recall that the sensor output sensitivity is given by S = B*L, where S is in units of volts per meter per second, B is field strength in Teslas, and L is active wire length in meters. If we pass current through the coil, the resultant motor force is f = S*I, where f is in newtons, and I is amperes. If we load the moving coil with the resistance of the coil in series with an external resistance, the generated voltage is E = S * v, and the current is I = E/R, so the resulting drag is c*v = S*I = S*E/R = S*(S*v)/R. So, c = S*S/R, where c is drag in newtons per meter per second. From the Feynman definitions, c = m * Gamma = m * Omega0 / Q. Since c from shunt damping is S^2 / R, we have the equality S *S / R = m * Omega0 / Q. Solving for Q, we obtain: Q = R * m * Omega0 / S^2 For a Q of unity, R = (Ps * S^2) / (2 * Pi * m), where Ps is sensor natural period in seconds. When I plug in my assumed values of Ps = 12 seconds, S = 85 v-s/m, and m = 0.1 kg, the value for R is 138 kOhms. In reality, the value I need to get a Q of 1.0 is less than half the above. I have no clue as to why. I calibrated the sensor output several ways, all yielding the same result. The mass was determined by weighing the solder wire mass and the coil assembly. To get better agreement, I would have to considerably decrease my value for S, which incidentally would also bring my calibrated seismic amplitudes into closer agreement with those recorded by station PAL. My present calibration gives me only 40% of the amplitude recorded at PAL. I hope someone out there can find a flaw in the mathematics. I am not happy with the apparent disagreement between theory and experiment. Cheers, Bob
Hi Chris,
 
  For a damped pendulum, we are dealing with the equation
 
  F =3D m(d2x/dt2) + c(dx/dt) + kx, where F is some forcing=20 function.
 
 m is mass, k is stiffness, and c is drag. Feynman defines=20 k=3Dm*Omega0^2, c=3Dm*Gamma, and Q=3DOmega0/Gamma, where Omega0 is the natur= al=20 frequency.
 
 In order to calculate the effect of a shunt load on the= =20 pickup coil for damping, recall that the sensor output sensitivity is given=20= by S=20 =3D B*L, where S is in units of volts per meter per second, B is field stren= gth in=20 Teslas, and L is active wire length in meters.
 
  If we pass current through the coil, the resultant motor force i= s f=20 =3D S*I, where f is in newtons, and I is amperes.
 
  If we load the moving coil with the resistance of the coil in se= ries=20 with an external resistance, the generated voltage is E =3D S * v, and the c= urrent=20 is I =3D E/R, so the resulting drag is c*v =3D S*I =3D S*E/R =3D S*(S*v)/R.<= /DIV>
 
  So, c =3D S*S/R, where c is drag in newtons per meter per second= .. From=20 the Feynman definitions, c =3D m * Gamma =3D m * Omega0 / Q. Since c from sh= unt=20 damping is S^2 / R, we have the equality S *S / R =3D m * Omega0 / Q.
 
  Solving for Q, we obtain:
 
Q =3D R * m * Omega0 / S^2
 
  For a Q of unity,
 
R =3D (Ps * S^2) / (2 * Pi * m), where Ps is sensor natural period in=20 seconds.
 
  When I plug in my assumed values of Ps =3D 12 seconds, S =3D 85=20= v-s/m,=20 and m =3D 0.1 kg, the value for R is 138 kOhms.
 
  In reality, the value I need to get a Q of 1.0 is less= =20 than half the above. I have no clue as to why. I calibrated the sensor outpu= t=20 several ways, all yielding the same result. The mass was determined by weigh= ing=20 the solder wire mass and the coil assembly. To get better agreement, I would= =20 have to considerably decrease my value for S, which incidentally would also=20 bring my calibrated seismic amplitudes into closer agreement with those reco= rded=20 by station PAL. My present calibration gives me only 40% of the amplitude=20 recorded at PAL.
 
  I hope someone out there can find a flaw in the mathematics. I a= m=20 not happy with the apparent disagreement between theory and experiment.
 
Cheers,
 
Bob
 
 
 Subject: Re: Korean nuclar test From: ChrisAtUpw@....... Date: Tue, 10 Oct 2006 00:04:40 EDT In a message dated 2006/10/09 , carpediem1@......... writes: > According to the news, the US has not confirmed that a nuclear device was > exploded, only that the event was equivalent to a large amount of TNT, but > below the kilo-ton level, a normal measurement for nuclear explosions. How far below a kilo ton? The Nagasaki bomb was about 20 kilo tons. Let's hope that it was a partial failure - or a chemical explosion !! Regards, Chris Chapman In a me= ssage dated 2006/10/09 , carpediem1@......... writes:

According to the news, the US h= as not confirmed that a nuclear device was
exploded, only that the event was equivalent to a large amount of TNT, but below the kilo-ton level, a normal measurement for nuclear explosions.

       How far below a kilo ton?

       The Nagasaki bomb was about 20 kilo ton= s.

       Let's hope that it was a partial failur= e - or a chemical explosion !!

       Regards,

       Chris Chapman Subject: Re: Building a lehman seismometer From: "tchannel" tchannel@.............. Date: Wed, 11 Oct 2006 08:57:28 -0600 Hi Chris, The sensor is coming along nicely. =20 Q. The coil is done, is it a good idea to coat the coil with glue or = something like that just to keep the wires from getting damaged, or is = it best just to leave it? Q. As the wires leave the coil and travel down the shaft to the lower = pivot, what is the best way to make the transition off the shaft to the = base? I have seen coiled wires to form a spring, to reduce drag on the = movement of the shaft. I have seen large loops and small coils. I = don't know if they should be hanging down or left and right. You must = have tried several different methods? Thanks, Ted ----- Original Message -----=20 From: ChrisAtUpw@.......... To: psn-l@................. Sent: Thursday, October 05, 2006 8:59 PM Subject: Re: Building a lehman seismometer In a message dated 2006/10/05, tchannel@.............. writes: I am in the process of building a sensor bases on your prototype, = and great drawings. I have most of the parts located, again with your = help and others on the mailing list. I will send pictures as I go along, = if you like, and if you tell me how to send them. Hi Ted, gif or jpg images would do fine to my EMail address. I regards to the angle between the bottom and top hinge, a fraction = of a degree, how do you measure for that? Or do you adjust and measure = the period, instead? I don't measure it, I calculate it. Then I make the structure = so that there is a small amount of adjustment. The axis is defined by = the centre of the ball and the edge of the top wire clamp. You vary the = slope of the long horizontal baseplate to set the period accurately, = using the end adjustment screw, but you keep the arm parallel to the = baseplate.=20 Chris, I see on your drawing you did not need to brace the vertical = arm of your device. Looks very strong. How did you attach that vertical = to the cross member? In my case the bottom of the vertical was milled flat and then = the centre sections were milled out ~15 thou so that there were four = longitudinal narrow strips about 1/16" wide x 3/4" long at the corners. = Then two bolts were put through the cross bar, the long base and = threaded into the vertical at the front and back ends. If you don't mill = out / file out the centre sections, the clamp force will be at the = centre, not at the edges where you want it and it will rock just enough = to give trouble. An alternative is to use a flat end and 3 or 4 shim = strips. You can also make three point suspensions, or you can glue the = vertical to the long base with two part modified acrylic glue. This is = strong and tough, unlike epoxy which is brittle. However you have to be = very quick as it has a gel time of about a couple of minutes in a warm = room.=20 An alternative construction might be to use a 3" dia tube for = the vertical? This can be held on either with a central vertical = threaded rod and a top plate, or by mounting a 3/4" circular rod = horizontally through two holes in the vertical tube, drilling and = tapping this and putting a vertical bolt up through the baseplate. You = would make three contact strip suspension flats at 120 deg. You can use an SS ball on a carbide flat lower hinge or crossed = cylinders. You can buy 1/8" solid tungsten carbide drills from = www.Smallparts.com or www.Digikey.com and cut the shanks to length with = a carbide disk. Glue one to the head of an SS bolt and the other to the = end of the arm with two part modified acrylic glue. I usually file a = shallow V first to locate the shank mechanically. Mount the vertical rod = or the ball on vertical support and the horizontal rod or the flat on = the arm, NOT the other way around! 8 thou Nickel plated piano wire is = available for mandolin strings at a music shop. See www.daddario.com Another method of construction which you might wish to consider? = In this I used Al alloy U channel, 3" wide x 1" high and three = triangular 3/16" to 1/4" thick corner plates at the end T / L joint. The = vertical is attached to the long horizontal base with two 5" corner = plates and four SS bolts per plate. I use two plain SS washers and a = spring washer per bolt to prevent it digging into the softer Al. The = open U is on the inside of the 90 deg joint. The cross bar is attached = to the outside of the vertical with four bolts and a 7" triangle. It = seems to work OK and makes quite a neat job. I bought it cut / chopped = to size, from a local metals supermarket. You maybe able to get 2" x 1" = U channel from building supplies / DIY. I tend to make things more = massive than absolutely necessary. The secret of the rigidity is mostly = in the three large triangular joint plates.=20 I tend to use 18" to 24" long tubular arms. 22" gives a 1.5 sec = basic pendulum which you can extend by x20 to 30 sec. 3 ft is a bit = bulky, but it gives maybe 40 sec or more? You can get compression = fittings for most tube. I use 1/2" SS water pipe and brass water = fittings, 15mm OD, but the tube may not be widely available? It is light = but rigid and non magnetic. Hard drawn Cu or brass are alternatives. You = can also buy general purpose brass compression 'engineering' fittings = for a wide range of standard pipe sizes, but these may only be available = through a few more specialist suppliers and they tend to be more = expensive than water fittings. Check on the availabilty of thin wall = welded SS water pipe?=20 Regards, Chris Chapman =20
Hi Chris,    The sensor = is coming=20 along nicely. 
Q.   The coil is done, is it = a good idea=20 to coat the coil with glue or something like that just to keep the wires = from=20 getting damaged, or is it best just to leave it?
Q.  As the wires leave the coil = and travel=20 down the shaft to the lower pivot, what is the best way to make the = transition=20 off the shaft to the base?  I have seen coiled wires to form a = spring, to=20 reduce drag on the movement of the shaft.  I have seen large loops = and=20 small coils.  I don't know if they should be hanging down or left = and=20 right.  You must have tried several different methods?
 
Thanks, Ted
 
 
 
----- Original Message -----
From:=20 ChrisAtUpw@.......
Sent: Thursday, October 05, = 2006 8:59=20 PM
Subject: Re: Building a lehman=20 seismometer

In a=20 message dated 2006/10/05, tchannel@..............=20 writes:

   I am in the process of building a sensor = bases on=20 your prototype, and great drawings. I have most of the parts = located, again=20 with your help and others on the mailing list. I will send pictures = as I go=20 along, if you like, and if you tell me how to send them.


Hi=20 Ted,

       gif or jpg images = would do=20 fine to my EMail address.

 I regards to the angle between the bottom and top hinge, = a=20 fraction of a degree, how do you measure for that? Or do you adjust = and=20 measure the period, instead?


       I don't=20 measure it, I calculate it. Then I make the structure so that there is = a small=20 amount of adjustment. The axis is defined by the centre of the ball = and the=20 edge of the top wire clamp. You vary the slope of the long horizontal=20 baseplate to set the period accurately, using the end adjustment = screw, but=20 you keep the arm parallel to the baseplate.

Chris, I see on your drawing you did not need to brace = the=20 vertical arm of your device. Looks very strong.  How did you = attach=20 that vertical to the cross member?


       In my=20 case the bottom of the vertical was milled flat and then the centre = sections=20 were milled out ~15 thou so that there were four longitudinal narrow = strips=20 about 1/16" wide x 3/4" long at the corners. Then two bolts were put = through=20 the cross bar, the long base and threaded into the vertical at the = front and=20 back ends. If you don't mill out / file out the centre sections, the = clamp=20 force will be at the centre, not at the edges where you want it and it = will=20 rock just enough to give trouble. An alternative is to use a flat end = and 3 or=20 4 shim strips.
       You can also = make three=20 point suspensions, or you can glue the vertical to the long base with = two part=20 modified acrylic glue. This is strong and tough, unlike epoxy which is = brittle. However you have to be very quick as it has a gel time of = about a=20 couple of minutes in a warm room. =
       An=20 alternative construction might be to use a 3" dia tube for the = vertical? This=20 can be held on either with a central vertical threaded rod and a top = plate, or=20 by mounting a 3/4" circular rod horizontally through two holes in the = vertical=20 tube, drilling and tapping this and putting a vertical bolt up through = the=20 baseplate. You would make three contact strip suspension flats at 120=20 deg.
       You can use an SS ball on = a=20 carbide flat lower hinge or crossed cylinders. You can buy 1/8" solid = tungsten=20 carbide drills from www.Smallparts.com or www.Digikey.com and cut the = shanks=20 to length with a carbide disk. Glue one to the head of an SS bolt and = the=20 other to the end of the arm with two part modified acrylic glue. I = usually=20 file a shallow V first to locate the shank mechanically. Mount the = vertical=20 rod or the ball on vertical support and the horizontal rod or the flat = on the=20 arm, NOT the other way around! 8 thou Nickel plated piano wire is = available=20 for mandolin strings at a music shop. See = www.daddario.com
    = Another method of = construction=20 which you might wish to consider? In this I used Al alloy U channel, = 3" wide x=20 1" high and three triangular 3/16" to 1/4" thick corner plates at the = end T /=20 L joint. The vertical is attached to the long horizontal base with two = 5"=20 corner plates and four SS bolts per plate. I use two plain SS washers = and a=20 spring washer per bolt to prevent it digging into the softer Al. The = open U is=20 on the inside of the 90 deg joint. The cross bar is attached to the = outside of=20 the vertical with four bolts and a 7" triangle. It seems to work OK = and makes=20 quite a neat job. I bought it cut / chopped to size, from a local = metals=20 supermarket. You maybe able to get 2" x 1" U channel from building = supplies /=20 DIY. I tend to make things more massive than absolutely necessary. The = secret=20 of the rigidity is mostly in the three large triangular joint plates.=20
    I tend to use 18" to 24" long tubular arms. 22" = gives a=20 1.5 sec basic pendulum which you can extend by x20 to 30 sec. 3 ft is = a bit=20 bulky, but it gives maybe 40 sec or more? You can get compression = fittings for=20 most tube. I use 1/2" SS water pipe and brass water fittings, 15mm OD, = but the=20 tube may not be widely available? It is light but rigid and non = magnetic. Hard=20 drawn Cu or brass are alternatives. You can also buy general purpose = brass=20 compression 'engineering' fittings for a wide range of standard pipe = sizes,=20 but these may only be available through a few more specialist = suppliers and=20 they tend to be more expensive than water fittings. Check on the = availabilty=20 of thin wall welded SS water pipe?

    = Regards,

    Chris=20 Chapman    =
Subject: Re: Building a lehman seismometer From: ChrisAtUpw@....... Date: Wed, 11 Oct 2006 14:52:43 EDT In a message dated 2006/10/11, tchannel@.............. writes: > Hi Chris, The sensor is coming along nicely. > Q. The coil is done, is it a good idea to coat the coil with glue or > something like that just to keep the wires from getting damaged, or is it best > just to leave it? Hi Ted, While it should be possible to varnish the coil, I have had nothing but trouble with this due to turns shorting out. I suggest that you leave it plain, but maybe wrap a length of 'self amalgamating' rubber tape around the outside. This rubber just sticks to itself, nothing else. Alternatively use paper or a cloth tape and a water based glue (no aromatic solvents). PVC tape tends to 'go sticky' and peel off after a few months. You may also be able to get large diameter heat shrink tube, but it tends to be expensive. > Q. As the wires leave the coil and travel down the shaft to the lower > pivot, what is the best way to make the transition off the shaft to the base? I > have seen coiled wires to form a spring, to reduce drag on the movement of > the shaft. I have seen large loops and small coils. I don't know if they > should be hanging down or left and right. You must have tried several different > methods? I mount a couple of solder pins on the coil former and then use thin shielded microphone cable from the coil to the hinge (and from the upright to the amplifier). Tie / tape it to the arm every 6" or so. Preferably look for the cable variety that has a black conducting plastic shield inside the braided copper screen. This gives the best performance / lowest noise - otherwise just use thin microphone cable. I use two bits of pinboard, each with 2 pins, one glued to the arm and one to the vertical. I use a V WIRE HAIRPINS about 2" long standing ~vertically of 36 / 38 gauge wire. I have not tried any thicker wire. You can use short coils, but you have to ensure that there are no turns touching. I use a polyurethane insulated magnet wire like Beldsol. I wrap a turn around the pin and then solder with a hot iron - or just solder the end 1/8" of wire, whichever is easier. The polyurethane insulation melts. It is easy to replace the wires. The apparatus / frame should be earthed. Regards, Chris Chapman In a me= ssage dated 2006/10/11, tchannel@.............. writes:

Hi Chris,    The= sensor is coming along nicely. 
Q.   The coil is done, is it a good idea to coat the coil with gl= ue or something like that just to keep the wires from getting damaged, or is= it best just to leave it?


 Hi Ted,

       While it should be possible to varnish=20= the coil, I have had nothing but trouble with this due to turns shorting out= .. I suggest that you leave it plain, but maybe wrap a length of 'self amalga= mating' rubber tape around the outside. This rubber just sticks to itself, n= othing else. Alternatively use paper or a cloth tape and a water based glue=20= (no aromatic solvents). PVC tape tends to 'go sticky' and peel off after a f= ew months. You may also be able to get large diameter heat shrink tube, but=20= it tends to be expensive.  

Q.  As the wires leave th= e coil and travel down the shaft to the lower pivot, what is the best way to= make the transition off the shaft to the base?  I have seen coiled wir= es to form a spring, to reduce drag on the movement of the shaft.  I ha= ve seen large loops and small coils.  I don't know if they should be ha= nging down or left and right. You must have tried several different methods?=


       I mount a couple of solder pins on the=20= coil former and then use thin shielded microphone cable from the coil to the= hinge (and from the upright to the amplifier). Tie / tape it to the arm eve= ry 6" or so. Preferably look for the cable variety that has a black conducti= ng plastic shield inside the braided copper screen. This gives the best perf= ormance / lowest noise - otherwise just use thin microphone cable.

       I use two bits of pinboard, each with 2= pins, one glued to the arm and one to the vertical. I use a V WIRE HAIRPINS= about 2" long standing ~vertically of 36 / 38 gauge wire. I have not tried=20= any thicker wire.
       You can use short coils, but you have t= o ensure that there are no turns touching.
       I use a polyurethane insulated magnet w= ire like Beldsol. I wrap a turn around the pin and then solder with a hot ir= on - or just solder the end 1/8" of wire, whichever is easier. The polyureth= ane insulation melts. It is easy to replace the wires.
       The apparatus / frame should be earthed= ..

       Regards,

       Chris Chapman Subject: Korean Nuclear test - Possible recording From: "Arie Verveer" greensky@.............. Date: Thu, 12 Oct 2006 20:18:25 +0800 Hi , I have posted some data that may show a recoding of the North Korean Nuclear event. The data values are very low and the recording may be noise. The calculated arrival times matches well. Alas the power failed on the arrival of the "S" wave. My system did record the Pakistan test a few years ago, though its signal to noise ratio was very low. Just a bump in a clear patch of data. Cheers Arie 061009.013926.au4.psn Mb4.2 8220km from Bickley, Western Australia __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Building a lehman seismometer From: "tchannel" tchannel@.............. Date: Thu, 12 Oct 2006 08:40:43 -0600 Hi Chris,=20 Q By V HAIRPINS, do you mean a piece of wire which forms a single "V" = shape? One for each wire, with no twist or turns? Q Just curious, about the magnet layout. Why are they arranged N,S on = the top and S,N on the bottom? If one used a horseshoe magnet it would be Just N,S Pictures tomorrow, I think. Thanks, Ted ----- Original Message -----=20 From: ChrisAtUpw@.......... To: psn-l@................. Sent: Wednesday, October 11, 2006 12:52 PM Subject: Re: Building a lehman seismometer In a message dated 2006/10/11, tchannel@.............. writes: Hi Chris, The sensor is coming along nicely. =20 Q. The coil is done, is it a good idea to coat the coil with glue = or something like that just to keep the wires from getting damaged, or = is it best just to leave it? Hi Ted, While it should be possible to varnish the coil, I have had = nothing but trouble with this due to turns shorting out. I suggest that = you leave it plain, but maybe wrap a length of 'self amalgamating' = rubber tape around the outside. This rubber just sticks to itself, = nothing else. Alternatively use paper or a cloth tape and a water based = glue (no aromatic solvents). PVC tape tends to 'go sticky' and peel off = after a few months. You may also be able to get large diameter heat = shrink tube, but it tends to be expensive. =20 Q. As the wires leave the coil and travel down the shaft to the = lower pivot, what is the best way to make the transition off the shaft = to the base? I have seen coiled wires to form a spring, to reduce drag = on the movement of the shaft. I have seen large loops and small coils. = I don't know if they should be hanging down or left and right. You must = have tried several different methods? I mount a couple of solder pins on the coil former and then use = thin shielded microphone cable from the coil to the hinge (and from the = upright to the amplifier). Tie / tape it to the arm every 6" or so. = Preferably look for the cable variety that has a black conducting = plastic shield inside the braided copper screen. This gives the best = performance / lowest noise - otherwise just use thin microphone cable.=20 I use two bits of pinboard, each with 2 pins, one glued to the = arm and one to the vertical. I use a V WIRE HAIRPINS about 2" long = standing ~vertically of 36 / 38 gauge wire. I have not tried any thicker = wire.=20 You can use short coils, but you have to ensure that there are = no turns touching. I use a polyurethane insulated magnet wire like Beldsol. I wrap = a turn around the pin and then solder with a hot iron - or just solder = the end 1/8" of wire, whichever is easier. The polyurethane insulation = melts. It is easy to replace the wires. The apparatus / frame should be earthed.=20 Regards, Chris Chapman
Hi Chris,
Q   By V HAIRPINS, do you = mean a piece of=20 wire which forms a single "V" shape?  One for each wire, with no = twist or=20 turns?
 
Q  Just curious, about the magnet=20 layout.  Why are they arranged N,S on the top and S,N on the=20 bottom?
If one used a horseshoe magnet it would = be Just=20 N,S
 
Pictures tomorrow, I think.   = Thanks,=20 Ted
----- Original Message -----
From:=20 ChrisAtUpw@.......
Sent: Wednesday, October 11, = 2006 12:52=20 PM
Subject: Re: Building a lehman=20 seismometer

In a=20 message dated 2006/10/11, tchannel@..............=20 writes:

Hi Chris,    The sensor is coming along=20 nicely. 
Q.   The coil is done, is it a good idea = to coat=20 the coil with glue or something like that just to keep the wires = from=20 getting damaged, or is it best just to leave it?

Hi=20 Ted,

       While it should be = possible=20 to varnish the coil, I have had nothing but trouble with this due to = turns=20 shorting out. I suggest that you leave it plain, but maybe wrap a = length of=20 'self amalgamating' rubber tape around the outside. This rubber just = sticks to=20 itself, nothing else. Alternatively use paper or a cloth tape and a = water=20 based glue (no aromatic solvents). PVC tape tends to 'go sticky' and = peel off=20 after a few months. You may also be able to get large diameter heat = shrink=20 tube, but it tends to be expensive.  

Q.  As the wires leave the coil and travel down the = shaft=20 to the lower pivot, what is the best way to make the transition off = the=20 shaft to the base?  I have seen coiled wires to form a spring, = to=20 reduce drag on the movement of the shaft.  I have seen large = loops and=20 small coils.  I don't know if they should be hanging down or = left and=20 right. You must have tried several different methods?

       I mount a = couple of=20 solder pins on the coil former and then use thin shielded microphone = cable=20 from the coil to the hinge (and from the upright to the amplifier). = Tie / tape=20 it to the arm every 6" or so. Preferably look for the cable variety = that has a=20 black conducting plastic shield inside the braided copper screen. This = gives=20 the best performance / lowest noise - otherwise just use thin = microphone=20 cable.

       I use two bits of=20 pinboard, each with 2 pins, one glued to the arm and one to the = vertical. I=20 use a V WIRE HAIRPINS about 2" long standing ~vertically of 36 / 38 = gauge=20 wire. I have not tried any thicker wire.=20
       You can use short coils, but = you have=20 to ensure that there are no turns=20 touching.
       I use a polyurethane = insulated magnet wire like Beldsol. I wrap a turn around the pin and = then=20 solder with a hot iron - or just solder the end 1/8" of wire, = whichever is=20 easier. The polyurethane insulation melts. It is easy to replace the=20 wires.
       The apparatus / frame = should be=20 earthed.

      =20 Regards,

       Chris = Chapman=20 Subject: Re: Building a lehman seismometer From: ChrisAtUpw@....... Date: Thu, 12 Oct 2006 15:23:50 EDT In a message dated 2006/10/12, tchannel@.............. writes: > Hi Chris, > Q By V HAIRPINS, do you mean a piece of wire which forms a single "V" > shape? One for each wire, with no twist or turns? Hi Ted, One ~straight piece of wire bent into a V / U shape with ~straight 2" sides and soldered to the pins at the ends, for each connection (like a hair pin). This works fine with the 36 AWG Cu wire that I use. > Q Just curious, about the magnet layout. Why are they arranged N,S on the > top and S,N on the bottom? > If one used a horseshoe magnet it would be Just N,S With a horse shoe magnet, you have to offset the position of the coil away from the poles, so that it experiences about 1/2 the maximum field. If the coil moves one way, the field increases, if it moves the other way the field decreases. But you are starting from the half field position and the field strength is ~S shaped - not very linear when the Lehman mass drifts in position! In my arrangement one winding of the coil moves in gap directly between a N pole on one face and a S pole on the other, carrying the full maximum field. You have opposite field directions for the two halves of the coil, so that the induced voltages add. This increases both the linearity and the output very considerably. The field strength is nearly constant anywhere over one pole. The return path from the back of the bar magnets is through the mild steel backing plates. Magnetically, this is a 'short circuit'. The N+S magnets only have to drive the external field across the central gap. You should get over 5x the field of an Alnico magnet. This allows the coil to be smaller while still giving an increased output. Another way of viewing the system is to consider the net field through the coil when it is centralised. You have two strong constant fields in opposite directions over the two halves, which balance out. Any movement applies a strong net field through the coil. Using the flat square NdFeB magnets makes this highly effective layout easy and inexpensive to achieve. Regards, Chris Chapman In a me= ssage dated 2006/10/12, tchannel@.............. writes:

Hi Chris,
Q   By V HAIRPINS, do you mean a piece of wire which forms a sing= le "V" shape?  One for each wire, with no twist or turns?

Hi Ted,

       One ~straight piece of wire bent into a= V / U shape with ~straight 2" sides and soldered to the pins at the ends, f= or each connection (like a hair pin). This works fine with the 36 AWG Cu wir= e that I use.

Q  Just curious, about th= e magnet layout. Why are they arranged N,S on the top and S,N on the bottom?=
If one used a horseshoe magnet it would be Just N,S


       With a horse shoe magnet, you have to o= ffset the position of the coil away from the poles, so that it experiences a= bout 1/2 the maximum field. If the coil moves one way, the field increases,=20= if it moves the other way the field decreases. But you are starting from the= half field position and the field strength is ~S shaped - not very linear w= hen the Lehman mass drifts in position!

       In my arrangement one winding of the co= il moves in gap directly between a N pole on one face and a S pole on the ot= her, carrying the full maximum field. You have opposite field directions for= the two halves of the coil, so that the induced voltages add. This increase= s both the linearity and the output very considerably. The field strength is= nearly constant anywhere over one pole.

       The return path from the back of the ba= r magnets is through the mild steel backing plates. Magnetically, this is a=20= 'short circuit'. The N+S magnets only have to drive the external field acros= s the central gap. You should get over 5x the field of an Alnico magnet. Thi= s allows the coil to be smaller while still giving an increased output.

       Another way of viewing the system is to= consider the net field through the coil when it is centralised. You have tw= o strong constant fields in opposite directions over the two halves, which b= alance out. Any movement applies a strong net field through the coil. Using=20= the flat square NdFeB magnets makes this highly effective layout easy and in= expensive to achieve.     

       Regards,

       Chris Chapman Subject: Sensor From: "tchannel" tchannel@.............. Date: Fri, 13 Oct 2006 15:12:11 -0600 Hi, I just wanted to let you all know I have finished my sensor. It = was patterned off the ideas and pictures from you folks. I have not tested it yet. I keep good records of the project, so If = anyone would like details or pictures just email me. Many thanks to Chris, and Bob for their ideas and help. And thanks to = all of you who took the time to answer so many of my questions. I let = you know how it works. Ted
Hi,  I just wanted to let you all = know I have=20 finished my sensor.  It was patterned off the ideas and pictures = from you=20 folks.
I have not tested it yet.   I = keep good=20 records of the project, so If anyone would like details or pictures just = email=20 me.
Many thanks to Chris, and Bob for their = ideas and=20 help.  And thanks to all of you who took the time to answer so many = of my=20 questions.   I let you know how it works.  =20 Ted
Subject: Intrest in Volcanos ? From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sat, 14 Oct 2006 04:57:01 +0000 Hi Is anyone here intrested in volcanos, along with earthquakes ? Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Intrest in Volcanos ? From: John Popelish jpopelish@........ Date: Sat, 14 Oct 2006 01:51:48 -0400 J=F3n Fr=EDmann wrote: > Hi >=20 > Is anyone here intrested in volcanos, along with earthquakes ?=20 I'm fascinated by them. Fortunately for me, there are many=20 web cams available so I can check in on many each day. i.e. http://www.nps.gov/archive/yell/oldfaithfulcam.htm http://hvo.wr.usgs.gov/cam/index.htm http://hvo.wr.usgs.gov/cam2/ http://www.fs.fed.us/gpnf/volcanocams/msh/images/mshvolcanocam.jpg http://www.geonet.org.nz/volcanocam.html http://www.avo.alaska.edu/webcam/a-spurr.jpg http://www.avo.alaska.edu/webcam/augtst.jpg http://www.avo.alaska.edu/webcam/veni.jpg __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Station Upgrde From: "Randy" rpratt@............. Date: Sat, 14 Oct 2006 08:41:11 -0500 Hi All, My lehmen has been inop for for some time after some power supply wires = shorted together and fried most everything including the computer ps and = motherboard. I have begun a rebuild with some changes and ideas = beginning with moving from EMON to Amaseis. I don't see instructions to = run multiple channels and I was wondering if this is possible? I tried = opening 2 copies in different directories and windows but the com port = conflicts. I have converted from the AD I constructed to a Dataq 154. =20 Randy
Hi All,
 
My lehmen has been inop for for = some time=20 after some power supply wires shorted together and fried most everything = including the computer ps and motherboard.  I have begun a = rebuild=20 with some changes and ideas beginning with moving from EMON to = Amaseis.  I=20 don't see instructions to run multiple channels and I was wondering if = this is=20 possible?  I tried opening 2 copies in different directories and = windows=20 but the com port conflicts.  I have converted from the AD I = constructed to=20 a Dataq 154. 
Randy
Subject: Re: Intrest in Volcanos ? From: Kim Barrow kimbarrow@....................... Date: Sat, 14 Oct 2006 08:03:35 -0700 (PDT) Hi Jon, Yes we are. I am the owner and founder of Earthquake Epi-Center located in the San Francisco Bay area (California.) I read yours and the other updates everyday on psn. We have a number of scientists on our boards at www.earthquakeepi-center.com Please feel free to post your thoughts, questions, comments on our website anytime. We are interested in all sorts of seismic & volcanic news. Sincerely Yours, Kim Barrow Jón Frímann wrote: Hi Is anyone here intrested in volcanos, along with earthquakes ? Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Hi Jon,
 
Yes we are. I am the owner and founder of Earthquake Epi-Center located in the San Francisco Bay area (California.)
 
I read yours and the other updates everyday on psn. We have a number of scientists on our boards at www.earthquakeepi-center.com
 
Please feel free to post your thoughts, questions, comments on our website anytime. We are interested in all sorts of seismic & volcanic news.
 
Sincerely Yours,
Kim Barrow


Jón Frímann <jonfr500@simnet.is> wrote:
Hi

Is anyone here intrested in volcanos, along with earthquakes ?

Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/

__________________________________________________________

Public Seismic Network Mailing List (PSN-L)

To leave this list email PSN-L-REQUEST@SEISMICNET.COM with
the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html for more information.

Subject: RE: Intrest in Volcanos ? From: "Bob Hancock" carpediem1@......... Date: Sat, 14 Oct 2006 08:19:23 -0700 Jon - Arizona State University (ASU) maintains a Volcano information log where they send out weekly updates on volcano activity world wide. They also = have other postings of interest. Here is the link to join the list: http://lists.asu.edu/cgi-bin/wa?SUBED1=3Dvolcano&A=3D1 Bob Hancock Three Points, AZ -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of J=F3n Fr=EDmann Sent: Friday, October 13, 2006 21:57 To: PSN-Postlist Subject: Intrest in Volcanos ? Hi Is anyone here intrested in volcanos, along with earthquakes ?=20 Regards. --=20 J=F3n Fr=EDmann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Intrest in Volcanos ? From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sat, 14 Oct 2006 19:25:25 +0000 Hi It is good to know that I am not alone in haveing intrest in volcanos here. I regulary record earthquakes from volcanos here in Iceland. But there are also four volcanos that are less then 100 km away from me and a dozen volcanos in less then 200 km away from me. Since I got my geophone there hasn't been a eruption. But I am sure that I won't have to wait long time until it does. I don't know if many of you are close to active volcanos. It would be intresting to get info on that. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Station Upgrde From: ChrisAtUpw@....... Date: Sat, 14 Oct 2006 17:19:16 EDT In a message dated 2006/10/14, rpratt@............. writes: > I don't see instructions to run multiple channels and I was wondering if > this is possible? I tried opening 2 copies in different directories and > windows but the com port conflicts. I have converted from the AD I constructed to > a Dataq 154. Hi Randy, Amaseis is single channel only. However, you can run two copies under Windows, but you would need two ADCs on different ports.... Maybe Alan will add a multi channel option sometime....? Regards, Chris Chapman In a me= ssage dated 2006/10/14, rpratt@............. writes:

I don't see instructions to ru= n multiple channels and I was wondering if this is possible?  I tried o= pening 2 copies in different directories and windows but the com port confli= cts.  I have converted from the AD I constructed to a Dataq 154.=

Hi Randy,

       Amaseis is single channel only. However= , you can run two copies under Windows, but you would need two ADCs on diffe= rent ports.... Maybe Alan will add a multi channel option sometime....?

       Regards,

       Chris Chapman Subject: Re: Interest in Volcanos ? From: Dave Nelson davenn@............... Date: Sun, 15 Oct 2006 10:58:54 +1000 Hi Jon, I have a great love of volcanoes, preferably up close and=20 personal. the list of volcanoes I have visited around the world, both active and=20 dormant, is slowly growing :) not to mention the dozens of extinct ones=20 specifically visited for samples and onsite study. where possible collecting rock/ash samples for study . Volcanoes ... location .......... active/dormant ..... yr/s= =20 visited Mt St Helens, Washington State, USA .... active... 1999 / 2006 Mt Ruapehu, Nth Island, New Zealand ..... active .... 1983 Mt Tongariro, Nth Island, New Zealand ..... active .... 1983 Mt Ngarahoe, Nth Island, New Zealand ..... active .... 1983 Mauna Kea, Hawai'i ........... acitve .... 1999 Ta'al Volcano, Luzon, Philippines ....... active .... 2000 / 2005 some longer term dormant ones but by no means extinct Mt Hood, Washington State, USA Mt Shasta, Oregon State, USA Mt Taranaki (Egmont), Nth Is, New Zealand, and a few photographed from a distance several others in the Philippines Lassen Peak', USA Mt Ranier, USA Truely extinct volcanoes ... The Dunedin Volcano and the others of the SE coast of the South Is.of= NZ. extensive study during my BSc studies The ones around Flagstaff, Arizona, USA Wishlist for visits ..... Vanuatu's active volcanoes other active ones in Philippines Indonesian volcanoes including Merapi and Anak Krakatoa Indonesia is paradise for volcano touring :) and ohhhhh if it wasnt for the hi cost ..... Japan... 3 main ones there would be Sakura jima. Fuji, and Unzen At 04:57 AM 14/10/2006 +0000, you wrote: >Hi >Is anyone here intrested in volcanos, along with earthquakes ? >Regards. >-- >J=F3n Fr=EDmann -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.408 / Virus Database: 268.13.4/476 - Release Date: 14/10/2006 __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Interest in Volcanos ? From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sun, 15 Oct 2006 01:13:23 +0000 Hi I've been to Hekla volcano here in Iceland. It was intresting and I got pictures from that trip. I also got few ask rocks from that mountin, really new one, problay not older then 10 or 20 years old. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Interest in Volcanos ? EDITED ! From: Dave Nelson davenn@............... Date: Sun, 15 Oct 2006 11:13:49 +1000 just an edit to correct a couple of serious mistakes in the last posting Hi Jon, I have a great love of volcanoes, preferably up close and=20 personal. the list of volcanoes I have visited around the world, both active and=20 dormant, is slowly growing :) not to mention the dozens of extinct ones=20 specifically visited for samples and onsite study. where possible collecting rock/ash samples for study . Volcanoes ... location .......... ..... yr/s visited Mt St Helens, Washington State, USA .... active... 1999 / 2006 Mt Ruapehu, Nth Island, New Zealand ..... active .... 1983 Mt Tongariro, Nth Island, New Zealand ..... active .... 1983 Mt Ngarahoe, Nth Island, New Zealand ..... active .... 1983 Kilauea Volcano, Hawai'i ........... active .... 1999 Ta'al Volcano, Luzon, Philippines ....... active .... 2000 / 2005 some longer term dormant ones but by no means extinct Mauna Kea, Hawai'i Mauna Loa, Hawai'i Mt Hood, Washington State, USA Mt Shasta, California State, USA Mt Taranaki (Egmont), Nth Is, New Zealand, and a few photographed from a distance several others in the Philippines Lassen Peak', USA Mt Ranier, USA Truely extinct volcanoes ... The Dunedin Volcano and the others of the SE coast of the South Is.of= NZ. extensive study during my BSc studies The ones around Flagstaff, Arizona, USA Wishlist for visits ..... Vanuatu's active volcanoes other active ones in Philippines Indonesian volcanoes including Merapi and Anak Krakatoa Indonesia is paradise for volcano touring :) and ohhhhh if it wasnt for the hi cost ..... Japan... 3 main ones there would be Sakura jima. Fuji, and Unzen Lifetime highlight ..... "playing" in the lava flows from Kilauea in 1999 scooping up 800 -1000 deg lava in soup ladels and other impliments Thanks to Tony, from the Big Island ... also a member of the PSN cheers Dave Nelson Sydney At 04:57 AM 14/10/2006 +0000, you wrote: >Hi >Is anyone here intrested in volcanos, along with earthquakes ? >Regards. >-- >J=F3n Fr=EDmann -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.408 / Virus Database: 268.13.4/476 - Release Date: 14/10/2006 __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Station Upgrade From: Bobhelenmcclure@....... Date: Sat, 14 Oct 2006 21:29:03 EDT On Sat, 14 Oct 2006 08:41:11 -0500, "Randy" writes, My lehmen has been inop for for some time after some power supply wires shorted together and fried most everything including the computer ps and motherboard. I have begun a rebuild with some changes and ideas beginning with moving from EMON to Amaseis. I don't see instructions to run multiple channels and I was wondering if this is possible? I tried opening 2 copies in different directories and windows but the com port conflicts. I have converted from the AD I constructed to a Dataq 154. Hi Randy, If you are using a Dataq device, you can log, filter, and heliplot display up to four channels, using my suite of software. You can also convert the WDQ files to Winquake PSN Type 4 files. See _http://www.jclahr.com/science/psn/mcclure/_ (http://www.jclahr.com/science/psn/mcclure/) and download "seismic_dataq.zip" Cheers, Bob
On Sat, 14 Oct 2006 08:41:11 -0500, "Randy" writes,
My lehmen has be= en=20 inop for for some time after some power supply wires
shorted together an= d=20 fried most everything including the computer ps and
motherboard.  I= =20 have begun a rebuild with some changes and ideas
beginning with moving f= rom=20 EMON to Amaseis.  I don't see instructions to
run multiple channels= and=20 I was wondering if this is possible?  I tried
opening 2 copies in=20 different directories and windows but the com port
conflicts.  I ha= ve=20 converted from the AD I constructed to a Dataq 154.
 
Hi Randy,
 
  If you are using a Dataq device, you can log, filter, and helipl= ot=20 display up to
four channels, using my suite of software. You can also con= vert=20 the WDQ
files to Winquake PSN Type 4 files.
 
  See http://www.jclahr.com/sc= ience/psn/mcclure/=20 and download "seismic_dataq.zip"
 
Cheers,
 
Bob
Subject: Large earthquake at hawaii island From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sun, 15 Oct 2006 17:51:23 +0000 Hi According to this there was just now a mag 6.3 earthquake at Hawaii Islands. See there, http://www.emsc-csem.org/index.php?page=current&sub=detail&id=35164 Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake at hawaii island From: ian ian@........... Date: Sun, 15 Oct 2006 21:08:05 +0100 looks like Tony (quakekona - psn member) is sitting right on top of it in Kona. Hope he's okay! Ian Jón Frímann wrote: >Hi > >According to this there was just now a mag 6.3 earthquake at Hawaii >Islands. See there, >http://www.emsc-csem.org/index.php?page=current&sub=detail&id=35164 > >Regards. > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake at hawaii island From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sun, 15 Oct 2006 20:48:01 +0000 Hi USGS now says the earthquake was mag 6.6 Mcd, while emsc-csem says it is Mw 6.5. According to new towns nearby the epicenter of this earthquake lost power and some mudslides have happened. I have been monitoring aftershocks on USGS webpage and based on that I am expecting at least one larger earthquake in the range of mag 5.5 - 6.5, based on that data. I might offcorse be wrong. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake at hawaii island From: Dave Nelson davenn@............... Date: Mon, 16 Oct 2006 07:01:21 +1000 a double whammy M6.6 mainshock and a M58 maj aftershock Dave N At 08:48 PM 15/10/2006 +0000, you wrote: >Hi > >USGS now says the earthquake was mag 6.6 Mcd, while emsc-csem says it is >Mw 6.5. According to new towns nearby the epicenter of this earthquake >lost power and some mudslides have happened. I have been monitoring >aftershocks on USGS webpage and based on that I am expecting at least >one larger earthquake in the range of mag 5.5 - 6.5, based on that data. >I might offcorse be wrong. > >Regards. >-- >J=F3n Fr=EDmann >http://www.jonfr.com >http://www.simnet.is/jonfr500/earthquake/ > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. > > > >-- >No virus found in this incoming message. >Checked by AVG Free Edition. >Version: 7.1.408 / Virus Database: 268.13.4/476 - Release Date: 14/10/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.408 / Virus Database: 268.13.4/476 - Release Date: 14/10/2006 __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake at hawaii island From: "Jerry Payton" gpayton880@....... Date: Sun, 15 Oct 2006 16:06:52 -0500 Here is FOX NEWS report on it: http://www.foxnews.com/story/0,2933,220977,00.html Jerry Payton ----- Original Message ----- From: Jón Frímann To: psn-l@.............. Sent: Sunday, October 15, 2006 3:48 PM Subject: Re: Large earthquake at hawaii island Hi USGS now says the earthquake was mag 6.6 Mcd, while emsc-csem says it is Mw 6.5. According to new towns nearby the epicenter of this earthquake lost power and some mudslides have happened. I have been monitoring aftershocks on USGS webpage and based on that I am expecting at least one larger earthquake in the range of mag 5.5 - 6.5, based on that data. I might offcorse be wrong. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) To leave this list email PSN-L-REQUEST@.............. with the body of the message (first line only): unsubscribe See http://www.seismicnet.com/maillist.html for more information.
Here is FOX NEWS report on it:
http://www.fo= xnews.com/story/0,2933,220977,00.html
 
Jerry Payton
----- Original Message -----
From:=20 J=F3n = Fr=EDmann=20
Sent: Sunday, October 15, 2006 = 3:48=20 PM
Subject: Re: Large earthquake = at hawaii=20 island

Hi

USGS now says the earthquake was mag 6.6 Mcd, = while=20 emsc-csem says it is
Mw 6.5. According to new towns nearby the = epicenter of=20 this earthquake
lost power and some mudslides have happened. I have = been=20 monitoring
aftershocks on USGS webpage and based on that I am = expecting at=20 least
one larger earthquake in the range of mag 5.5 - 6.5, based on = that=20 data.
I might offcorse be wrong.

Regards.
--
J=F3n=20 Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/j= onfr500/earthquake/

__________________________________________= ________________

Public=20 Seismic Network Mailing List (PSN-L)

To leave this list email = PSN-L-REQUEST@............... =20 with
the body of the message (first line only): unsubscribe
See = http://www.seismicnet.co= m/maillist.html=20 for more information.
Subject: Re: Large earthquake at hawaii island From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sun, 15 Oct 2006 21:12:05 +0000 Hi Here is a news about this earthquake from BBC News. http://news.bbc.co.uk/1/hi/world/americas/6053796.stm Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake at hawaii island From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sun, 15 Oct 2006 22:29:00 +0000 Hi I also hope that Tony is ok. According to news there are alot of power outrage in Hawaii at the moment becose of the earthquake. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake at hawaii island From: peaches@............ Date: Sun, 15 Oct 2006 14:43:58 -1000 (HST) Hi all. Im ok. Thanks for your concern. Just a few minor injuries reported on the island so far. Ive just posed my data for the main shock and the main aftershock. Both are hopelessly clipped to give an accurate WQ magnitude. There have been rock slides here and there on the island along with some homes and structures being damaged. There has been a state-wide power outage, incl Honolulu. Our power just came back on about an hour ago so things are starting to get back to normal. We had lots of breakage mostly in the kitchen from dishes, glasses etc being thrown from the cabinets. My 19" tv was thrown from the shelf and smashed. It was truly frightning I must say. It felt like a 7. or better from here, only 9 miles away. It was hard to stand. Most of the energy was in an E-W direction as things facing that direction were thrown the most. Anyway, once again, thank you all for your concern. Aloha Tony Potenzo Hawaii Psn > Hi > > I also hope that Tony is ok. According to news there are alot of power > outrage in Hawaii at the moment becose of the earthquake. > > Regards. > -- > Jón Frímann > http://www.jonfr.com > http://www.simnet.is/jonfr500/earthquake/ > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake at hawaii island From: Kim Barrow kimbarrow@....................... Date: Sun, 15 Oct 2006 17:56:34 -0700 (PDT) Hi Peaches, I wanted to say I'm glad to hear you're okay too! We have family vacationing on the Island of Hawaii...what timing huh. This is a copy of my message I posted earlier at EARTHQUAKE EPI-CENTER . Take care, Kim ____________________________________________________ From: http://www.websitetoolbox.com/tool/post/earthquake/vpost?id=1448264&trail=15#1 KimLosGatosCA Today at 04:28 PM --------------------------------- Hi Everyone, Family members visiting Hawaii called to say they had no power and widespread damage. Magnitude 6.6 ISLAND OF HAWAII, HAWAII October 15, 2006 http://quake.wr.usgs.gov/ Possible pre shocks? 2005 07 17-Hawaii region, Hawaii- M5.2 2005 07 15-Hawaii region,Hawaii- M5.3 Information obtained at: http://earthquake.usgs.gov/regional/world/historical.php Please be prepared to evacuate away from low lying areas near coastal waters in the event a stronger quake occurs and a tsunami warning is issued. We want to extend our best wishes to everyone involved in this mornings major quake a speedy recovery. NOTE: There is a likely hood of sizable west coast quake is possible if history repeats itself...more on this probability to follow. Take care, Kim peaches@............ wrote: Hi all. Im ok. Thanks for your concern. Just a few minor injuries reported on the island so far. Ive just posed my data for the main shock and the main aftershock. Both are hopelessly clipped to give an accurate WQ magnitude. There have been rock slides here and there on the island along with some homes and structures being damaged. There has been a state-wide power outage, incl Honolulu. Our power just came back on about an hour ago so things are starting to get back to normal. We had lots of breakage mostly in the kitchen from dishes, glasses etc being thrown from the cabinets. My 19" tv was thrown from the shelf and smashed. It was truly frightning I must say. It felt like a 7. or better from here, only 9 miles away. It was hard to stand. Most of the energy was in an E-W direction as things facing that direction were thrown the most. Anyway, once again, thank you all for your concern. Aloha Tony Potenzo Hawaii Psn > Hi > > I also hope that Tony is ok. According to news there are alot of power > outrage in Hawaii at the moment becose of the earthquake. > > Regards. > -- > Jón Frímann > http://www.jonfr.com > http://www.simnet.is/jonfr500/earthquake/ > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Hi Peaches,
 
I wanted to say I'm glad to hear you're okay too!
 
We have family vacationing on the Island of Hawaii...what timing huh.
 
This is a copy of my message I posted earlier at EARTHQUAKE EPI-CENTER .
 
Take care,
Kim
____________________________________________________
 
 
KimLosGatosCA

 

 
Unread post Today at 04:28 PM     
Hi Everyone,
Family members visiting Hawaii called to say they had no power and widespread damage.
 
Magnitude 6.6 ISLAND OF HAWAII, HAWAII October 15, 2006
http://quake.wr.usgs.gov/ 
 
Possible pre shocks? 2005 07 17-Hawaii region, Hawaii- M5.2 2005 07 15-Hawaii region,Hawaii- M5.3
Information obtained at:
 
Please be prepared to evacuate away from low lying areas near coastal waters in the event a stronger quake occurs and a tsunami warning is issued.
 
We want to extend our best wishes to everyone involved in this mornings major quake a speedy recovery.
 
NOTE: There is a likely hood of sizable west coast quake is possible if history repeats itself...more on this probability to follow.
 
Take care,
Kim


peaches@............ wrote:
Hi all.

Im ok. Thanks for your concern. Just a few minor injuries reported
on the island so far.
Ive just posed my data for the main shock and the main aftershock.
Both are hopelessly clipped to give an accurate WQ magnitude.
There have been rock slides here and there on the island along with
some homes and structures being damaged. There has been a state-wide
power outage, incl Honolulu. Our power just came back on about an hour
ago so things are starting to get back to normal. We had lots of breakage
mostly in the kitchen from dishes, glasses etc being thrown from the
cabinets. My 19" tv was thrown from the shelf and smashed.
It was truly frightning I must say. It felt like a 7. or better from here,
only 9 miles away. It was hard to stand. Most of the energy was in an E-W
direction as things facing that direction were thrown the most.
Anyway, once again, thank you all for your concern.

Aloha
Tony Potenzo
Hawaii Psn

> Hi
>
> I also hope that Tony is ok. According to news there are alot of power
> outrage in Hawaii at the moment becose of the earthquake.
>
> Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>


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Subject: Re: Digest from 10/14/2006 00:00:34 From: "Randy" rpratt@............. Date: Sun, 15 Oct 2006 20:47:43 -0500 Thanks Bob, It looks like you have proven the feasability of running multichannels from one AD in 2 or more windows. Couldn't the same logic go into Amaseis quite easily? Now I need some things to plug into more channels. Randy ----- Original Message ----- From: To: Sent: Sunday, October 15, 2006 2:01 AM Subject: Digest from 10/14/2006 00:00:34 > > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 1 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Station Upgrde > From: "Randy" > Date: Sat, 14 Oct 2006 08:41:11 -0500 > > This is a multi-part message in MIME format. > > ------=_NextPart_000_0008_01C6EF6C.807B2BA0 > Content-Type: text/plain; > charset="iso-8859-1" > Content-Transfer-Encoding: quoted-printable > > Hi All, > > My lehmen has been inop for for some time after some power supply wires = > shorted together and fried most everything including the computer ps and = > motherboard. I have begun a rebuild with some changes and ideas = > beginning with moving from EMON to Amaseis. I don't see instructions to = > run multiple channels and I was wondering if this is possible? I tried = > opening 2 copies in different directories and windows but the com port = > conflicts. I have converted from the AD I constructed to a Dataq 154. =20 > Randy > ------=_NextPart_000_0008_01C6EF6C.807B2BA0 > Content-Type: text/html; > charset="iso-8859-1" > Content-Transfer-Encoding: quoted-printable > > > > charset=3Diso-8859-1"> > > > > >
Hi All,
>
 
>
My lehmen has been inop for for = > some time=20 > after some power supply wires shorted together and fried most everything = > > including the computer ps and motherboard.  I have begun a = > rebuild=20 > with some changes and ideas beginning with moving from EMON to = > Amaseis.  I=20 > don't see instructions to run multiple channels and I was wondering if = > this is=20 > possible?  I tried opening 2 copies in different directories and = > windows=20 > but the com port conflicts.  I have converted from the AD I = > constructed to=20 > a Dataq 154. 
>
Randy
> > ------=_NextPart_000_0008_01C6EF6C.807B2BA0-- > > > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 2 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Re: Intrest in Volcanos ? > From: Kim Barrow > Date: Sat, 14 Oct 2006 08:03:35 -0700 (PDT) > > --0-5202789-1160838215=:91705 > Content-Type: text/plain; charset=iso-8859-1 > Content-Transfer-Encoding: 8bit > > Hi Jon, > > Yes we are. I am the owner and founder of Earthquake Epi-Center located in the San Francisco Bay area (California.) > > I read yours and the other updates everyday on psn. We have a number of scientists on our boards at www.earthquakeepi-center.com > > Please feel free to post your thoughts, questions, comments on our website anytime. We are interested in all sorts of seismic & volcanic news. > > Sincerely Yours, > Kim Barrow > > > Jón Frímann wrote: > Hi > > Is anyone here intrested in volcanos, along with earthquakes ? > > Regards. > -- > Jón Frímann > http://www.jonfr.com > http://www.simnet.is/jonfr500/earthquake/ > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > > --0-5202789-1160838215=:91705 > Content-Type: text/html; charset=iso-8859-1 > Content-Transfer-Encoding: 8bit > >
Hi Jon,
 
Yes we are. I am the owner and founder of Earthquake Epi-Center located in the San Francisco Bay area (California.)
 
I read yours and the other updates everyday on psn. We have a number of scientists on our boards at www.earthquakeepi-center.com
 
Please feel free to post your thoughts, questions, comments on our website anytime. We are interested in all sorts of seismic & volcanic news.
 
>
Sincerely Yours,
Kim Barrow


Jón Frímann <jonfr500@.........> wrote:
Hi

Is anyone here intrested in volcanos, along with earthquakes ?

Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/

__________________________________________________________

Pu blic Seismic Network Mailing List (PSN-L)

To leave this list email PSN-L-REQUEST@.............. with
the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html for more information.

> --0-5202789-1160838215=:91705-- > > > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 3 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: RE: Intrest in Volcanos ? > From: "Bob Hancock" > Date: Sat, 14 Oct 2006 08:19:23 -0700 > > Jon - > > Arizona State University (ASU) maintains a Volcano information log where > they send out weekly updates on volcano activity world wide. They also = > have > other postings of interest. > > Here is the link to join the list: > > http://lists.asu.edu/cgi-bin/wa?SUBED1=3Dvolcano&A=3D1 > > Bob Hancock > Three Points, AZ > > -----Original Message----- > From: psn-l-request@.............. [mailto:psn-l-request@............... = > On > Behalf Of J=F3n Fr=EDmann > Sent: Friday, October 13, 2006 21:57 > To: PSN-Postlist > Subject: Intrest in Volcanos ? > > Hi > > Is anyone here intrested in volcanos, along with earthquakes ?=20 > > Regards. > --=20 > J=F3n Fr=EDmann > http://www.jonfr.com > http://www.simnet.is/jonfr500/earthquake/ > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with=20 > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > > > > > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 4 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Re: Intrest in Volcanos ? > From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= > Date: Sat, 14 Oct 2006 19:25:25 +0000 > > Hi > > It is good to know that I am not alone in haveing intrest in volcanos > here. I regulary record earthquakes from volcanos here in Iceland. But > there are also four volcanos that are less then 100 km away from me and > a dozen volcanos in less then 200 km away from me. Since I got my > geophone there hasn't been a eruption. But I am sure that I won't have > to wait long time until it does. > > I don't know if many of you are close to active volcanos. It would be > intresting to get info on that. > > Regards. > -- > Jón Frímann > http://www.jonfr.com > http://www.simnet.is/jonfr500/earthquake/ > > > > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 5 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Re: Station Upgrde > From: ChrisAtUpw@....... > Date: Sat, 14 Oct 2006 17:19:16 EDT > > > --part1_c72.25e6ab7.3262ae54_boundary > Content-Type: text/plain; charset="US-ASCII" > Content-Transfer-Encoding: 7bit > > In a message dated 2006/10/14, rpratt@............. writes: > > > I don't see instructions to run multiple channels and I was wondering if > > this is possible? I tried opening 2 copies in different directories and > > windows but the com port conflicts. I have converted from the AD I constructed to > > a Dataq 154. > > Hi Randy, > > Amaseis is single channel only. However, you can run two copies under > Windows, but you would need two ADCs on different ports.... Maybe Alan will > add a multi channel option sometime....? > > Regards, > > Chris Chapman > > --part1_c72.25e6ab7.3262ae54_boundary > Content-Type: text/html; charset="US-ASCII" > Content-Transfer-Encoding: quoted-printable > > In a me= > ssage dated 2006/10/14, rpratt@............. writes:
>
>
: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px"> I don't see instructions to ru= > n multiple channels and I was wondering if this is possible?  I tried o= > pening 2 copies in different directories and windows but the com port confli= > cts.  I have converted from the AD I constructed to a Dataq 154.= > " SIZE=3D3 PTSIZE=3D12 FAMILY=3D"SANSSERIF" FACE=3D"Arial" LANG=3D"0"> KQUOTE>
> #ffffff" SIZE=3D2 PTSIZE=3D10 FAMILY=3D"SANSSERIF" FACE=3D"Arial" LANG=3D"0"= > >
> Hi Randy,
>
>        Amaseis is single channel only. However= > , you can run two copies under Windows, but you would need two ADCs on diffe= > rent ports.... Maybe Alan will add a multi channel option sometime....?
>
>        Regards,
>
>        Chris Chapman > > --part1_c72.25e6ab7.3262ae54_boundary-- > > > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 6 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Re: Interest in Volcanos ? > From: Dave Nelson > Date: Sun, 15 Oct 2006 10:58:54 +1000 > > > Hi Jon, > I have a great love of volcanoes, preferably up close and=20 > personal. > the list of volcanoes I have visited around the world, both active and=20 > dormant, > is slowly growing :) not to mention the dozens of extinct ones=20 > specifically visited > for samples and onsite study. > where possible collecting rock/ash samples for study . > > Volcanoes ... location .......... active/dormant ..... yr/s= > =20 > visited > Mt St Helens, Washington State, USA .... active... 1999 / 2006 > Mt Ruapehu, Nth Island, New Zealand ..... active .... 1983 > Mt Tongariro, Nth Island, New Zealand ..... active .... 1983 > Mt Ngarahoe, Nth Island, New Zealand ..... active .... 1983 > Mauna Kea, Hawai'i ........... acitve .... 1999 > Ta'al Volcano, Luzon, Philippines ....... active .... 2000 / 2005 > > some longer term dormant ones but by no means extinct > > Mt Hood, Washington State, USA > Mt Shasta, Oregon State, USA > Mt Taranaki (Egmont), Nth Is, New Zealand, > > and a few photographed from a distance > several others in the Philippines > Lassen Peak', USA > Mt Ranier, USA > > Truely extinct volcanoes ... > > The Dunedin Volcano and the others of the SE coast of the South Is.of= > NZ. > extensive study during my BSc studies > The ones around Flagstaff, Arizona, USA > > Wishlist for visits ..... > > Vanuatu's active volcanoes > other active ones in Philippines > Indonesian volcanoes including Merapi and Anak Krakatoa > Indonesia is paradise for volcano touring :) > and ohhhhh if it wasnt for the hi cost ..... Japan... > 3 main ones there would be Sakura jima. Fuji, and Unzen > > > > > At 04:57 AM 14/10/2006 +0000, you wrote: > >Hi > >Is anyone here intrested in volcanos, along with earthquakes ? > >Regards. > >-- > >J=F3n Fr=EDmann > > > > -- > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.1.408 / Virus Database: 268.13.4/476 - Release Date: 14/10/2006 > > > > > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 7 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Re: Interest in Volcanos ? > From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= > Date: Sun, 15 Oct 2006 01:13:23 +0000 > > Hi > > I've been to Hekla volcano here in Iceland. It was intresting and I got > pictures from that trip. I also got few ask rocks from that mountin, > really new one, problay not older then 10 or 20 years old. > > Regards. > -- > Jón Frímann > http://www.jonfr.com > http://www.simnet.is/jonfr500/earthquake/ > > > > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 8 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Re: Interest in Volcanos ? EDITED ! > From: Dave Nelson > Date: Sun, 15 Oct 2006 11:13:49 +1000 > > > just an edit to correct a couple of serious mistakes in the last posting > > Hi Jon, > I have a great love of volcanoes, preferably up close and=20 > personal. > the list of volcanoes I have visited around the world, both active and=20 > dormant, > is slowly growing :) not to mention the dozens of extinct ones=20 > specifically visited > for samples and onsite study. > where possible collecting rock/ash samples for study . > > Volcanoes ... location .......... ..... yr/s visited > Mt St Helens, Washington State, USA .... active... 1999 / 2006 > Mt Ruapehu, Nth Island, New Zealand ..... active .... 1983 > Mt Tongariro, Nth Island, New Zealand ..... active .... 1983 > Mt Ngarahoe, Nth Island, New Zealand ..... active .... 1983 > Kilauea Volcano, Hawai'i ........... active .... 1999 > Ta'al Volcano, Luzon, Philippines ....... active .... 2000 / 2005 > > some longer term dormant ones but by no means extinct > Mauna Kea, Hawai'i > Mauna Loa, Hawai'i > Mt Hood, Washington State, USA > Mt Shasta, California State, USA > Mt Taranaki (Egmont), Nth Is, New Zealand, > > and a few photographed from a distance > several others in the Philippines > Lassen Peak', USA > Mt Ranier, USA > > Truely extinct volcanoes ... > > The Dunedin Volcano and the others of the SE coast of the South Is.of= > NZ. > extensive study during my BSc studies > The ones around Flagstaff, Arizona, USA > > Wishlist for visits ..... > > Vanuatu's active volcanoes > other active ones in Philippines > Indonesian volcanoes including Merapi and Anak Krakatoa > Indonesia is paradise for volcano touring :) > and ohhhhh if it wasnt for the hi cost ..... Japan... > 3 main ones there would be Sakura jima. Fuji, and Unzen > > > > Lifetime highlight ..... "playing" in the lava flows from Kilauea in 1999 > scooping up 800 -1000 deg lava in soup ladels and other impliments > > Thanks to Tony, from the Big Island ... also a member of the PSN > > cheers > Dave Nelson > Sydney > > > At 04:57 AM 14/10/2006 +0000, you wrote: > >Hi > >Is anyone here intrested in volcanos, along with earthquakes ? > >Regards. > >-- > >J=F3n Fr=EDmann > > > > -- > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.1.408 / Virus Database: 268.13.4/476 - Release Date: 14/10/2006 > > > > > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 9 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Re: Station Upgrade > From: Bobhelenmcclure@....... > Date: Sat, 14 Oct 2006 21:29:03 EDT > > > -------------------------------1160875743 > Content-Type: text/plain; charset="US-ASCII" > Content-Transfer-Encoding: 7bit > > On Sat, 14 Oct 2006 08:41:11 -0500, "Randy" writes, > My lehmen has been inop for for some time after some power supply wires > shorted together and fried most everything including the computer ps and > motherboard. I have begun a rebuild with some changes and ideas > beginning with moving from EMON to Amaseis. I don't see instructions to > run multiple channels and I was wondering if this is possible? I tried > opening 2 copies in different directories and windows but the com port > conflicts. I have converted from the AD I constructed to a Dataq 154. > > Hi Randy, > > If you are using a Dataq device, you can log, filter, and heliplot display > up to > four channels, using my suite of software. You can also convert the WDQ > files to Winquake PSN Type 4 files. > > See _http://www.jclahr.com/science/psn/mcclure/_ > (http://www.jclahr.com/science/psn/mcclure/) and download "seismic_dataq.zip" > > Cheers, > > Bob > > -------------------------------1160875743 > Content-Type: text/html; charset="US-ASCII" > Content-Transfer-Encoding: quoted-printable > > > > > > Arial"=20 > bottomMargin=3D7 leftMargin=3D7 topMargin=3D7 rightMargin=3D7> e_document=20 > face=3DArial color=3D#000000 size=3D2> >
On Sat, 14 Oct 2006 08:41:11 -0500, "Randy" writes,
My lehmen has be= > en=20 > inop for for some time after some power supply wires
shorted together an= > d=20 > fried most everything including the computer ps and
motherboard.  I= > =20 > have begun a rebuild with some changes and ideas
beginning with moving f= > rom=20 > EMON to Amaseis.  I don't see instructions to
run multiple channels= > and=20 > I was wondering if this is possible?  I tried
opening 2 copies in=20 > different directories and windows but the com port
conflicts.  I ha= > ve=20 > converted from the AD I constructed to a Dataq 154.
>
 
>
Hi Randy,
>
 
>
  If you are using a Dataq device, you can log, filter, and helipl= > ot=20 > display up to
four channels, using my suite of software. You can also con= > vert=20 > the WDQ
files to Winquake PSN Type 4 files.
>
 
>
  See href=3D"http://www.jclahr.com/science/psn/mcclure/">http://www.jclahr.com/sc = > ience/psn/mcclure/=20 > and download "seismic_dataq.zip"
>
 
>
Cheers,
>
 
>
Bob
> > -------------------------------1160875743-- > > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-DIGEST-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake at hawaii island From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Mon, 16 Oct 2006 02:06:46 +0000 Hi It is good to hear that you are ok Tony and your family. The damage can be repared. What is worring for me is when I am looking at the aftershock pattern, it appears to be slow and few smaller aftershocks that I was expecting. I find that rater strange, The earthquake that did follow straigt after the main quake is something that I have seen before, but the same thing did happen in Iceland, when a Ms 6.5 earthquake did hit SIZS (south Iceland) in Iceland. I am still exspecting at least one mag 5.5 aftershock, based on the ideas I have on how this large type of earthquakes changes the crust around the epicenter. I am also bit intrested if there has been any changes in volcano activite, since this earthquake is large enugh to change volcano activite. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Station Upgrde From: John or Jan Lahr JohnJan@........ Date: Sun, 15 Oct 2006 21:34:27 -0700 At 06:41 AM 10/14/2006, you wrote: >Hi All, > >My lehmen has been inop for for some time after some power supply >wires shorted together and fried most everything including the >computer ps and motherboard. I have begun a rebuild with some >changes and ideas beginning with moving from EMON to Amaseis. I >don't see instructions to run multiple channels and I was wondering >if this is possible? I tried opening 2 copies in different >directories and windows but the com port conflicts. I have >converted from the AD I constructed to a Dataq 154. >Randy Hi Randy, I think you should be able to run two copies of AmaSeis, each out of its own directory, and each looking at a different com port. Is that what you tried to do? John Lahr __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake at hawaii island From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Mon, 16 Oct 2006 18:54:35 +0000 Hi I saw today that USGS has upgraded the size of this earthquake to Mw6.7. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: What happened at 17:40 to 17:50 UT on Oct 15th? From: George Bush ke6pxp@....... Date: Mon, 16 Oct 2006 12:59:36 -0700 Hello- I was wondering if anyone else detected a strong signal in the background to the M6.7 Hawaii Is. quake? It is visible on the N-S and E-W signals, and is strongest on my vertical detector, but the frequency is higher and different than the event at 17:07:48??? You can go to the PSN web and see my signal at 061015.170749.srz \quakes\0610\061015.170019.srz.psn. I was not able to find any event in the above time frame that could have caused this (the M5.4 at 17:14 happened too soon to be what I saw)??? It could have been something local, but it was much stronger than any normal road traffic noise I detect from a nearby road. I would appreciate any ideas or thoughts as to what I detected. George Bush Sea Ranch, CA, USA 38.73775N, 123.48882W __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: What happened at 17:40 to 17:50 UT on Oct 15th? From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Mon, 16 Oct 2006 20:07:02 +0000 Hi I did take a look at the signal. It appears to be local noise, on E-W and N-S it wanish when I lowpassfilter the signal to 1Hz, on Z the signal shows when I lowpass it to 1Hz. But it cuts into the surfise waves that you are recording. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: What happened at 17:40 to 17:50 UT on Oct 15th? From: George Bush ke6pxp@....... Date: Mon, 16 Oct 2006 13:33:38 -0700 Thank you J=F3n,=20 You are probably right, but I was hoping it was a nearby quake. At 08:07 PM 10/16/2006 +0000, you wrote: >Hi > >I did take a look at the signal. It appears to be local noise, on E-W >and N-S it wanish when I lowpassfilter the signal to 1Hz, on Z the >signal shows when I lowpass it to 1Hz. But it cuts into the surfise >waves that you are recording. > >Regards. >--=20 >J=F3n Fr=EDmann >http://www.jonfr.com >http://www.simnet.is/jonfr500/earthquake/ > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with=20 >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. > George __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake at hawaii island From: peaches@............ Date: Mon, 16 Oct 2006 16:16:12 -1000 (HST) Hi Jon To answer your question about the volcano, the HVO reports are saying that there is no change in eruptive activity so far. However large quakes have been known to alter the "plumbing" and change eruptive patterns. We are pretty much back to normal here. Also, no appreciable aftershocks today so far. We did have a couple tiny ones in the wee morning hours tho. Anyway, check out http://hvo.wr.usgs.gov/kilauea/update/main.html for the latest updates and deformation charts of our volcanoes. Im just finishing recording the surface waves from the New Britian event. Will be posting it soon. Thanks for writing and take care. Aloha Tony > Hi > > It is good to hear that you are ok Tony and your family. The damage can > be repared. What is worring for me is when I am looking at the > aftershock pattern, it appears to be slow and few smaller aftershocks > that I was expecting. I find that rater strange, The earthquake that did > follow straigt after the main quake is something that I have seen > before, but the same thing did happen in Iceland, when a Ms 6.5 > earthquake did hit SIZS (south Iceland) in Iceland. I am still > exspecting at least one mag 5.5 aftershock, based on the ideas I have on > how this large type of earthquakes changes the crust around the > epicenter. > > I am also bit intrested if there has been any changes in volcano > activite, since this earthquake is large enugh to change volcano > activite. > > Regards. > -- > Jón Frímann > http://www.jonfr.com > http://www.simnet.is/jonfr500/earthquake/ > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Unusual signal on Northern Cal. Seismometers From: kpayea@........... Date: Mon, 16 Oct 2006 20:04:16 -0700 Hello All, especially those of you in Northern California. The alarm went off on my system a few minutes ago, and the signal on the screen was very unusual. It was a decent sized sine wave, about 20 second period. I thought it might be local, caused by heavy construction on 101 nearby, but most of the Berkeley network instruments at http://www.ncedc.org/bdsn/quicklook.html show the same thing. To my eye, this doesn't look like a normal EQ signal. Or is it just me? The signal is still ringing down, after a good 25 minutes. What do you all think? Cheers, Keith Keith Payea Bryant Labs kpayea@.............. www.bryantlabs.net (707) 566-8935
Hello = All,=20 especially those of you in Northern California.  The alarm went off = on my=20 system a few minutes ago, and the signal on the screen was very = unusual. =20 It was a decent sized sine wave, about 20 second period.  I thought = it=20 might be local, caused by heavy construction on 101 nearby, but most of = the=20 Berkeley network instruments at http://www.nce= dc.org/bdsn/quicklook.html =20 show the same thing.  To my eye, this doesn't look like a normal EQ = signal.  Or is it just me?
 
The = signal is still=20 ringing down, after a good 25 minutes.
 
What = do you all=20 think?
 
Cheers,
 
 
    Keith
 
Keith=20 Payea
Bryant Labs
kpayea@..............
www.bryantlabs.net
(707)=20 566-8935
 
Subject: Re: Unusual signal on Northern Cal. Seismometers From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Tue, 17 Oct 2006 03:09:36 +0000 Hi Based on raw data from emsc-csem, there appears to have been earthquake near cost of Japan. There was a mag 6.6 near New Britain earliar this night. See here, http://www.emsc-csem.org/index.php?page=current&sub=detail&id=35211 Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Unusual signal on Northern Cal. Seismometers From: Stephen & Kathy skmort@............ Date: Mon, 16 Oct 2006 20:22:44 -0700 FYI,, your seeing the surface waves from the New Britain quake! On my system, east of Sacramento, they are approx. 18 seconds,,, my system started recording the surface waves at approx. 02:08:22 UTC = 19:08:22 PDT ! Stephen PSN Station #55 kpayea@........... wrote: > Hello All, especially those of you in Northern California. The alarm > went off on my system a few minutes ago, and the signal on the screen > was very unusual. It was a decent sized sine wave, about 20 second > period. I thought it might be local, caused by heavy construction on > 101 nearby, but most of the Berkeley network instruments at > http://www.ncedc.org/bdsn/quicklook.html > show the same > thing. To my eye, this doesn't look like a normal EQ signal. Or is > it just me? > > The signal is still ringing down, after a good 25 minutes. > > What do you all think? > > Cheers, > > > /Keith/ > > Keith Payea > Bryant Labs > kpayea@.............. > www.bryantlabs.net > (707) 566-8935 > FYI,,   your seeing the surface waves from the New Britain quake!
On my system, east of Sacramento, they are approx. 18 seconds,,,  my system started recording the surface waves at approx. 02:08:22 UTC = 19:08:22 PDT !
  Stephen
  PSN Station #55

kpayea@........... wrote:
Hello All, especially those of you in Northern California.  The alarm went off on my system a few minutes ago, and the signal on the screen was very unusual.  It was a decent sized sine wave, about 20 second period.  I thought it might be local, caused by heavy construction on 101 nearby, but most of the Berkeley network instruments at http://www.ncedc.org/bdsn/quicklook.html  show the same thing.  To my eye, this doesn't look like a normal EQ signal.  Or is it just me?
 
The signal is still ringing down, after a good 25 minutes.
 
What do you all think?
 
Cheers,
 
 
    Keith
 
Keith Payea
Bryant Labs
(707) 566-8935
 
Subject: Re: Unusual signal on Northern Cal. Seismometers From: Pete Rowe ptrowe@......... Date: Mon, 16 Oct 2006 20:39:27 -0700 (PDT) I recorded the signal here in San Jose but my alarm didn't go off. I don't think I have the trigger paramenters set correctly. Any suggestions for setting the trigger level? Pete --- Stephen & Kathy wrote: > FYI,, your seeing the surface waves from the New > Britain quake! > On my system, east of Sacramento, they are approx. > 18 seconds,,, my > system started recording the surface waves at > approx. 02:08:22 UTC = > 19:08:22 PDT ! > Stephen > PSN Station #55 > > kpayea@........... wrote: > > Hello All, especially those of you in Northern > California. The alarm > > went off on my system a few minutes ago, and the > signal on the screen > > was very unusual. It was a decent sized sine > wave, about 20 second > > period. I thought it might be local, caused by > heavy construction on > > 101 nearby, but most of the Berkeley network > instruments at > > http://www.ncedc.org/bdsn/quicklook.html > > > > show the same > > thing. To my eye, this doesn't look like a normal > EQ signal. Or is > > it just me? > > > > The signal is still ringing down, after a good 25 > minutes. > > > > What do you all think? > > > > Cheers, > > > > > > /Keith/ > > > > Keith Payea > > Bryant Labs > > kpayea@.............. > > > www.bryantlabs.net > > (707) 566-8935 > > > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Long period sensor plan From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Tue, 17 Oct 2006 03:45:41 +0000 Hi Here is my first long period sensor plan. This sensor is simple and I hope that this idea is workable. Here is a raw drawing of the sensor, this is just a draft. The picture is quite large. http://www.simnet.is/jonfr500/sensor/long.period.sensor.v1.0.jpg Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Unusual signal on Northern Cal. Seismometers From: Stephen & Kathy skmort@............ Date: Mon, 16 Oct 2006 21:05:52 -0700 If you have a software alarm, others will have to help,,, I have a hardware alarm which monitors the input to the A/D and is adjusted right at the largest of the storm wave energy we get along the N. Cal coast! Stephen PSN Station #55 Pete Rowe wrote: > I recorded the signal here in San Jose but my alarm > didn't go off. I don't think I have the trigger > paramenters set correctly. Any suggestions for setting > the trigger level? > Pete > > --- Stephen & Kathy wrote: > > >> FYI,, your seeing the surface waves from the New >> Britain quake! >> On my system, east of Sacramento, they are approx. >> 18 seconds,,, my >> system started recording the surface waves at >> approx. 02:08:22 UTC = >> 19:08:22 PDT ! >> Stephen >> PSN Station #55 >> >> kpayea@........... wrote: >> >>> Hello All, especially those of you in Northern >>> >> California. The alarm >> >>> went off on my system a few minutes ago, and the >>> >> signal on the screen >> >>> was very unusual. It was a decent sized sine >>> >> wave, about 20 second >> >>> period. I thought it might be local, caused by >>> >> heavy construction on >> >>> 101 nearby, but most of the Berkeley network >>> >> instruments at >> >>> http://www.ncedc.org/bdsn/quicklook.html >>> >>> >> >> show the same >> >>> thing. To my eye, this doesn't look like a normal >>> >> EQ signal. Or is >> >>> it just me? >>> >>> The signal is still ringing down, after a good 25 >>> >> minutes. >> >>> >>> What do you all think? >>> >>> Cheers, >>> >>> >>> /Keith/ >>> >>> Keith Payea >>> Bryant Labs >>> kpayea@.............. >>> >> >> >>> www.bryantlabs.net >>> (707) 566-8935 >>> >>> > > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > > If you have a software alarm, others will have to help,,,   I have a hardware alarm which monitors the input to the A/D and is adjusted right at the largest of the storm wave energy we get along the N. Cal coast!
  Stephen
  PSN Station #55

Pete Rowe wrote: 
I recorded the signal here in San Jose but my alarm
didn't go off. I don't think I have the trigger
paramenters set correctly. Any suggestions for setting
the trigger level?
Pete

--- Stephen & Kathy <skmort@............> wrote:

  
FYI,,   your seeing the surface waves from the New
Britain quake!
On my system, east of Sacramento, they are approx.
18 seconds,,,  my 
system started recording the surface waves at
approx. 02:08:22 UTC = 
19:08:22 PDT !
  Stephen
  PSN Station #55

kpayea@........... wrote:
    
Hello All, especially those of you in Northern
      
California.  The alarm 
    
went off on my system a few minutes ago, and the
      
signal on the screen 
    
was very unusual.  It was a decent sized sine
      
wave, about 20 second 
    
period.  I thought it might be local, caused by
      
heavy construction on 
    
101 nearby, but most of the Berkeley network
      
instruments at 
    
http://www.ncedc.org/bdsn/quicklook.html 

      
<BLOCKED::http://www.ncedc.org/bdsn/quicklook.html> 
show the same 
    
thing.  To my eye, this doesn't look like a normal
      
EQ signal.  Or is 
    
it just me?
 
The signal is still ringing down, after a good 25
      
minutes.
    
 
What do you all think?
 
Cheers,
 
 
    /Keith/
 
Keith Payea
Bryant Labs
kpayea@..............
      
<mailto:kpayea@..............>
    
www.bryantlabs.net <http://www.bryantlabs.net/>
(707) 566-8935
 
      


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Subject: Questions From: "tchannel" tchannel@.............. Date: Tue, 17 Oct 2006 12:30:51 -0600 I have finished my sensor, and have had it running for three days. 1. During the night hours, 11pm to 6am, the tract goes from normal to = noisy, getting worse each hour. The sensor sits in the garage on a = concrete slab. No draft and no heat. As soon as I go into the garage = in the AM and the room gets warmer, because the sun warms the room to = about 60 f. The trace returns to normal. Is this temperature effect? I = also turn off the monitor and turn it back on in the AM. Could the CTR = or the computer create noise? They set about three feet from the sensor. = Again no heat, no draft and nothing running out there in the night. 2. I think I am getting a good recording, I have see the last two = quakes and to me they look normal. I am in Boise Idaho and have tried to compare my .PSN with any others = close by. However our local one in Boise is down and the next, nearest = one is in Washington State. Now here is a hard question to ask: I = created my expanded trace, using the same time plotted on the .PSN in = Washington (061017.013725.ebgz.psn M6.5 10356km from Ellensburg, Wa.,) = This was around one hour of trace. I did this so I could compare the = two side by side. I was a little surprised to see the Wa. psn to show a = large spike on the P and a short spike on the S. My trace looks very = similar, but I show a large spike on the S and a smaller spike on the P. = From the description of the Ellensburg Wa file it has a Z in it, is = that a Vertical sensor? and since my sensor is a Horz pointing N/S, = would that explain the different. These events came from the East, and I = have my beam pointing North. Anyone who would like me to send both .PSN's to them for a critique, = please email me. I would appreciate someone looking at them and = voicing an opinion as to my level of gain, not sure if it is correct, = and some advise as to how to best filter this event to enhance the P and = S. I am just using trial and error. 3. Presently I am building a Plexiglas box. But would it help to = reduce noise if I built a second box wrapped with alum foil? Or other = ideas on building a box which would make a positive different? 4. I know weather can alter the way the trace looks, I thought my = situation was weather, but it was clear today. What is there in a front moving thru that creates the noise? Lets say = a front with little wind and no lightening. Many thanks, Ted
I have finished my sensor, and have had = it running=20 for three days.
 
1.  During the night hours, 11pm = to 6am, the=20 tract goes from normal to noisy, getting worse each hour.  The = sensor sits=20 in the garage on a concrete slab.  No draft and no heat.  As = soon as I=20 go into the garage in the AM and the room gets warmer, because the = sun=20 warms the room to about 60 f. The trace returns to normal.  Is this = temperature effect?  I also turn off the monitor and turn it back = on in the=20 AM.  Could the CTR or the computer create noise? They set about = three feet=20 from the sensor. Again no heat, no draft and nothing running out there = in the=20 night.
 
2.   I think I am getting a = good=20 recording, I have see the last two quakes and to me they look=20 normal.
I am in Boise Idaho and have tried to = compare my=20 ..PSN with any others close by.  However our local one in Boise is = down and=20 the next, nearest one is in Washington State.   Now here is a = hard=20 question to ask:  I created my expanded trace, using the same time = plotted=20 on the .PSN in Washington (061017.013725.ebgz.psn M6.5 10356km from Ellensburg, Wa.,) = This was=20 around one hour of trace.  I did this so I could compare the two = side by=20 side.  I was a little surprised to see the Wa. psn to show a large = spike on=20 the P and a short spike on the S.  My trace looks very similar, but = I show=20 a large spike on the S and a smaller spike on the P.   From = the=20 description of the Ellensburg Wa file it has a Z in it, is that a = Vertical=20 sensor? and since my sensor is a Horz pointing N/S, would that explain = the=20 different. These events came from the East, and I have my beam pointing=20 North.
Anyone who would like me to send both .PSN's to them for a = critique, please=20 email me.   I would appreciate someone looking at them and = voicing an=20 opinion as to my level of gain, not sure if it is correct, and some = advise as to=20 how to best filter this event to enhance the P and S. I am just using = trial and=20 error.
 
3.  Presently I am building a = Plexiglas=20 box.  But would it help to reduce noise if I built a second box = wrapped=20 with alum foil?   Or other ideas on building a box which would = make a=20 positive different?
 
4.   I know weather can alter = the way the=20 trace looks, I thought my situation was weather, but it was clear=20 today.
What is there in a front moving thru = that creates=20 the noise?   Lets say a front with little wind and no=20 lightening.
 
Many thanks, = Ted
Subject: Re: Questions From: John Popelish jpopelish@........ Date: Tue, 17 Oct 2006 17:17:41 -0400 tchannel wrote: (snip) > 3. Presently I am building a Plexiglas box. > But would it help to reduce noise if I built > a second box wrapped with alum foil? > Or other ideas on building a box which would make a positive different? Though it is nice to look through a Plexiglass box, it is not a very good thermal performer. you can buy a 4 by 8 foot sheet of foam insulation form any builder's supply, including possibly one that has a foil surface. This can be cut into rectangles and fit together into a very light weight and thermally insulating box for a fraction of the cost of a Plexiglass one. Add a night light or other small heat source to the top, inside, to stratify the temperature inside the box, to suppress convection currents at night, when the floor is warmer than the air. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Questions From: ChrisAtUpw@....... Date: Tue, 17 Oct 2006 17:28:20 EDT In a message dated 2006/10/17, tchannel@.............. writes: > I have finished my sensor, and have had it running for three days. Hi Ted, Sorry, but you haven't finished your sensor until you have evaluated and proved it!! > 1. During the night hours, 11pm to 6am, the tract goes from normal to > noisy, getting worse each hour. The sensor sits in the garage on a concrete slab. > No draft and no heat. This is the evening cooling problem due to air convection. You need to house the seismometer in a thermally insulated case and place a heater giving about 10 Watts inside the top. I use two Al cased power resistors bolted to a sheet of Al. This maintains a positive vertical internal temperature gradient at all times and suppresses convection. Make the enclosure out of 2" Celotex. This has fibre glass skins and Al foil top coats. Tape the joins with 3" gaffer tape and glue the joints with foam grouting. You can make double windows with either photocopy film or cellulose sheet. See http://pages.prodigy.net/fxc/seiscoverslg.jpg More work, but 100% essential! > 2. I think I am getting a good recording, I have see the last two quakes > and to me they look normal. > I am in Boise Idaho and have tried to compare my .PSN with any others close > by. However our local one in Boise is down and the next, nearest one is in > Washington State. Now here is a hard question to ask: I created my expanded > trace, using the same time plotted on the .PSN in Washington ( > 061017.013725.ebgz.psn M6.5 10356km from Ellensburg, Wa.,) This was around one hour of trace. > I did this so I could compare the two side by side. I was a little > surprised to see the Wa. psn to show a large spike on the P and a short spike on the > S. My trace looks very similar, but I show a large spike on the S and a > smaller spike on the P. From the description of the Ellensburg Wa file it has a > Z in it, is that a Vertical sensor? and since my sensor is a Horz pointing > N/S, would that explain the different. Z signifies a vertical sensor. The two other designations are E east and N north, both true, not magnetic. The P and Rayleigh waves are predominantly vertical, so a Lehman, which is a horizontal sensor, will have a low sensitivity to them. The S and Love waves are horizontal and you should see relatively large signals. The amplitude of the signals also depends both on the type and on the angular range. > I would appreciate someone looking at them and voicing an opinion as to my > level of gain, not sure if it is correct, and some advise as to how to best > filter this event to enhance the P and S. I suggest that you set the lowpass filter at 2 Hz and the highpass filter at 0.4 Hz, both at least 4 pole. > 3. Presently I am building a Plexiglas box. See my previous EMail and the advice above. You need a thermally insulated enclosure with sealed joints and a top heater, probably not a perspex box. > 4. I know weather can alter the way the trace looks, I thought my situation > was weather, but it was clear today. > What is there in a front moving thru that creates the noise? Lets say a > front with little wind and no lightning. Cold fronts tend to give more seismic noise that warm fronts. All fronts have wind and turbulence / pressure variations associated with them, at altitude, if not so much at ground level. Broad band wind noise is a common seismic problem. Regards, Chris Chapman In a message dated 2006/10/17, tcha= nnel@.............. writes:

I have finished my sensor, and=20= have had it running for three days.


Hi Ted,

       Sorry, but you haven't finished your se= nsor until you have evaluated and proved it!!

1.  During the night hour= s, 11pm to 6am, the tract goes from normal to noisy, getting worse each hour= .. The sensor sits in the garage on a concrete slab. No draft and no heat.&nb= sp;


       This is the evening cooling problem du= e to air convection. You need to house the seismometer in a thermally insula= ted case and place a heater giving about 10 Watts inside the top. I use two=20= Al cased power resistors bolted to a sheet of Al. This maintains a positive=20= vertical internal temperature gradient at all times and suppresses convectio= n. Make the enclosure out of 2" Celotex. This has fibre glass skins and Al f= oil top coats. Tape the joins with 3" gaffer tape and glue the joints with f= oam grouting. You can make double windows with either photocopy film or cell= ulose sheet. See http://pages.prodigy.net/fxc/seiscoverslg.jpg More work, bu= t 100% essential!

2.   I think I am get= ting a good recording, I have see the last two quakes and to me they look no= rmal.
I am in Boise Idaho and have tried to compare my .PSN with any others close= by.  However our local one in Boise is down and the next, nearest one=20= is in Washington State.  Now here is a hard question to ask: I created=20= my expanded trace, using the same time plotted on the .PSN in Washington (061017.013725.ebgz.psn M6.5 10356km from Ellensburg, Wa.,) This was=20= around one hour of trace.  I did this so I could compare the two side b= y side.  I was a little surprised to see the Wa. psn to show a large sp= ike on the P and a short spike on the S.  My trace looks very similar,=20= but I show a large spike on the S and a smaller spike on the P. From the des= cription of the Ellensburg Wa file it has a Z in it, is that a Vertical sens= or? and since my sensor is a Horz pointing N/S, would that explain the diffe= rent.


       Z signifies a vertical sensor. The two= other designations are E east and N north, both true, not magnetic. The P a= nd Rayleigh waves are predominantly vertical, so a Lehman, which is a horizo= ntal sensor, will have a low sensitivity to them. The S and Love waves are h= orizontal and you should see relatively large signals. The amplitude of the=20= signals also depends both on the type and on the angular range.
  
I would appreciate some= one looking at them and voicing an opinion as to my level of gain, not sure=20= if it is correct, and some advise as to how to best filter this event to enh= ance the P and S.


       I suggest that you set the lowpass fil= ter at 2 Hz and the highpass filter at 0.4 Hz, both at least 4 pole.<= FONT COLOR=3D"#000000" BACK=3D"#ffffff" style=3D"BACKGROUND-COLOR: #ffffff"= SIZE=3D3 PTSIZE=3D12 FAMILY=3D"SERIF" FACE=3D"Times New Roman" LANG=3D"0"><= BR>
3.  Presently I am buildi= ng a Plexiglas box.


       See my previous EMail and the advice a= bove. You need a thermally insulated enclosure with sealed joints and a top=20= heater, probably not a perspex box.

4. I know weather can alter the= way the trace looks, I thought my situation was weather, but it was clear t= oday.
What is there in a front moving thru that creates the noise?  Lets say= a front with little wind and no lightning.


       Cold fronts tend to give more seismic n= oise that warm fronts. All fronts have wind and turbulence / pressure variat= ions associated with them, at altitude, if not so much at ground level. Broa= d band wind noise is a common seismic problem.

       Regards,

       Chris Chapman Subject: Re: Long period sensor plan From: ChrisAtUpw@....... Date: Tue, 17 Oct 2006 20:48:16 EDT In a message dated 2006/10/17, jonfr500@......... writes: > Here is my first long period sensor plan. This sensor is simple and I > hope that this idea is workable. Here is a raw drawing of the sensor, > this is just a draft. The picture is quite large. > http://www.simnet.is/jonfr500/sensor/long.period.sensor.v1.0.jpg Hi Jon, I'm sorry, but I don't understand your drawing. What are the component parts and how is it supposed to work? Regards, Chris Chapman In a me= ssage dated 2006/10/17, jonfr500@......... writes:

Here is my first long period se= nsor plan. This sensor is simple and I
hope that this idea is workable. Here is a raw drawing of the sensor,
this is just a draft. The picture is quite large.
http://www.simnet.is/jonfr500/sensor/long.period.sensor.v1.0.jpg

Hi Jon,

       I'm sorry, but I don't understand your=20= drawing. What are the component parts and how is it supposed to work?

       Regards,

       Chris Chapman Subject: Re: Long period sensor plan From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Wed, 18 Oct 2006 01:53:10 +0000 Hi This is just a first draw of the sensor. The basic idea comes from the lehman type of seismometer. I have already moved the dapming to the front of the coil and the magnets. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Questions From: "Geoffrey" gmvoeth@........... Date: Wed, 18 Oct 2006 04:52:24 -0700 Hello Ted; The file 061017.013725.ebgz.psn is way too noisy. The gain should be reduced to the point where noise is only +/- a few counts. This signal reminds me of the Hawaii quake I received but instead of getting any S wave I just got two "P" waves (Main event/aftershock) and what seemed to be followed by surface waves. note: I have found that Winquake does not want me to start my converted files on a decimal point I must start my files on an exact second start point to get correct times. If I start my files in the middle of a second it will offset all the measured times with an error by the decimal amount. Winquake seems to ignore fractional values smaller than the whole second at the start of a data set. Dont know if I am clear here. Regards; geoff ----- Original Message ----- From: "tchannel" To: Sent: Tuesday, October 17, 2006 11:30 AM Subject: Questions I have finished my sensor, and have had it running for three days. 1. During the night hours, 11pm to 6am, the tract goes from normal to noisy, getting worse each hour. The sensor sits in the garage on a concrete slab. No draft and no heat. As soon as I go into the garage in the AM and the room gets warmer, because the sun warms the room to about 60 f. The trace returns to normal. Is this temperature effect? I also turn off the monitor and turn it back on in the AM. Could the CTR or the computer create noise? They set about three feet from the sensor. Again no heat, no draft and nothing running out there in the night. 2. I think I am getting a good recording, I have see the last two quakes and to me they look normal. I am in Boise Idaho and have tried to compare my .PSN with any others close by. However our local one in Boise is down and the next, nearest one is in Washington State. Now here is a hard question to ask: I created my expanded trace, using the same time plotted on the .PSN in Washington (061017.013725.ebgz.psn M6.5 10356km from Ellensburg, Wa.,) This was around one hour of trace. I did this so I could compare the two side by side. I was a little surprised to see the Wa. psn to show a large spike on the P and a short spike on the S. My trace looks very similar, but I show a large spike on the S and a smaller spike on the P. From the description of the Ellensburg Wa file it has a Z in it, is that a Vertical sensor? and since my sensor is a Horz pointing N/S, would that explain the different. These events came from the East, and I have my beam pointing North. Anyone who would like me to send both .PSN's to them for a critique, please email me. I would appreciate someone looking at them and voicing an opinion as to my level of gain, not sure if it is correct, and some advise as to how to best filter this event to enhance the P and S. I am just using trial and error. 3. Presently I am building a Plexiglas box. But would it help to reduce noise if I built a second box wrapped with alum foil? Or other ideas on building a box which would make a positive different? 4. I know weather can alter the way the trace looks, I thought my situation was weather, but it was clear today. What is there in a front moving thru that creates the noise? Lets say a front with little wind and no lightening. Many thanks, Ted __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Questions From: ChrisAtUpw@....... Date: Wed, 18 Oct 2006 09:41:45 EDT In a message dated 2006/10/18, gmvoeth@........... writes: > Hello Ted; > The file 061017.013725.ebgz.psn is way too noisy. The gain should be reduced > to the point where noise is only +/- a few counts. > > This signal reminds me of the Hawaii quake I received but instead of getting > any S wave I just got two "P" waves (Main event/aftershock) and what seemed > to be followed by surface waves. Hi Geoff, Ted, This advice is not correct. Ted has a Lehman which senses the microseismic background of 0.5 to 15 microns amplitude as well as quake signals. Ted will want to sense longer period quakes which are a small fraction of this amplitude and to filter them out, so he needs the background to be at least 100 counts. Regards, Chris Chapman In a me= ssage dated 2006/10/18, gmvoeth@........... writes:

Hello Ted;
The file 061017.013725.ebgz.psn is way too noisy. The gain should be reduced=
to the point where noise is only +/- a few counts.

This signal reminds me of the Hawaii quake I received but instead of getting= any S wave I just got two "P" waves (Main event/aftershock) and what seemed=
to be followed by surface waves.


Hi Geoff, Ted,

       This advice is not correct. Ted has a L= ehman which senses the microseismic background of 0.5 to 15 microns amplitud= e as well as quake signals. Ted will want to sense longer period quakes whic= h are a small fraction of this amplitude and to filter them out, so he needs= the background to be at least 100 counts. 

       Regards,

       Chris Chapman Subject: Re: Questions From: "tchannel" tchannel@.............. Date: Wed, 18 Oct 2006 09:15:58 -0600 Hi Folks, For those who are new to these subjects, here is my case = study on a specific problem, and the group's advise which fixed it. = With my new station setup and running, the trace would get progressively = noisier, starting at 11:00pm until 8:00am. This noise was huge, the trace started out, looking like a pencil line = and then,would progress to something like the teeth of a saw, so large = it would almost touch the line above and below. As the room went back to = day time temp, so did the trace quite down. The garage, where it sat, has no heat and no drafts. The temp in the = garage, at night, would get to 40-50 and during the day 60's. Because I had not finished my cover/box the sensor sat on the floor open = to the air. I was advised to build a box which would protect the sensor = from air currents and thermos. So last night, temporarily, I covered = the sensor using two sawhorses and two blankets. The trace remained = perfectly still all night As a newcomer to these issues, I had no idea the importance of these = enclosures. I noticed if I waved my hand or made any movements, which = created air movement I would see a spike. I did not realize that = invisible air currents in the room, caused by the different in floor vs. = air temperature, would cause huge noise. Thanks for the guidance. Q 1. I understand that some people orient their sensor N/S others E/W, = Are the sensors ever oriented at a 45 degree angle between the two? Q 2. What are the expectations of a Lehman sensor? I know that depends = on many factors, and not the lease of which is the quality of the = sensor, and its environment, as well as the type and location of the = events. But just in general terms. The AS1, which is not a Lehman = suggest one should be able to see 6.0m from several thousand mile away, = or something like that. The reason I ask, I do hear statements, both over and under my = expectations. Time will tell, but I wanted your opinions. Cheers, Ted ----- Original Message -----=20 From: ChrisAtUpw@.......... To: psn-l@................. Sent: Wednesday, October 18, 2006 7:41 AM Subject: Re: Questions In a message dated 2006/10/18, gmvoeth@........... writes: Hello Ted; The file 061017.013725.ebgz.psn is way too noisy. The gain should be = reduced to the point where noise is only +/- a few counts. This signal reminds me of the Hawaii quake I received but instead of = getting any S wave I just got two "P" waves (Main event/aftershock) and = what seemed to be followed by surface waves. Hi Geoff, Ted, This advice is not correct. Ted has a Lehman which senses the = microseismic background of 0.5 to 15 microns amplitude as well as quake = signals. Ted will want to sense longer period quakes which are a small = fraction of this amplitude and to filter them out, so he needs the = background to be at least 100 counts. =20 Regards, Chris Chapman
Hi Folks,    For = those who are=20 new to these subjects, here is my case study on a specific problem, and = the=20 group's advise which fixed it.  With my new station setup and = running, the=20 trace would get progressively noisier, starting at 11:00pm until=20 8:00am.
This noise was huge, the trace started = out, looking=20 like a pencil line and then,would progress to something like the teeth = of a saw,=20 so large it would almost touch the line above and below. As the room = went back=20 to day time temp, so did the trace quite down.
The garage, where it sat, has no heat = and no=20 drafts.  The temp in the garage, at night, would get to 40-50 and = during=20 the day 60's.
 
Because I had not finished my cover/box = the sensor=20 sat on the floor open to the air.  I was advised to build a box = which would=20 protect the sensor from air currents and thermos. So last night,=20 temporarily, I  covered the sensor using two sawhorses and two = blankets. The trace remained perfectly still all night
 
As a newcomer to these issues, I had no = idea the=20 importance of these enclosures.  I noticed if I waved my hand or = made=20 any  movements, which created air movement I would see a = spike.  I did=20 not realize that invisible air currents in the room, caused by the = different in=20 floor vs. air temperature, would cause huge noise.
 
Thanks for the guidance.
 
Q 1.  I understand that some = people=20 orient their sensor N/S others E/W,  Are the sensors ever oriented = at a 45=20 degree angle between the two?
 
Q 2. What are the expectations of a = Lehman=20 sensor?  I know that depends on many factors, and not the lease of = which is=20 the quality of the sensor, and its environment, as well as the type and = location=20 of the events.  But just in general terms. The AS1, which is not a = Lehman=20 suggest one should be able to see 6.0m from several thousand mile away, = or=20 something like that.
The reason I ask, I do hear statements, = both over=20 and under my expectations.  Time will tell, but I wanted your=20 opinions.
 
Cheers, Ted
 
 
 
 
----- Original Message -----
From:=20 ChrisAtUpw@.......
Sent: Wednesday, October 18, = 2006 7:41=20 AM
Subject: Re: Questions

In a=20 message dated 2006/10/18, gmvoeth@........... = writes:

Hello Ted;
The file 061017.013725.ebgz.psn is way too = noisy.=20 The gain should be reduced
to the point where noise is only +/- a = few=20 counts.

This signal reminds me of the Hawaii quake I received = but=20 instead of getting any S wave I just got two "P" waves (Main=20 event/aftershock) and what seemed
to be followed by surface=20 waves.


Hi Geoff,=20 Ted,

       This advice is not = correct.=20 Ted has a Lehman which senses the microseismic background of 0.5 to 15 = microns=20 amplitude as well as quake signals. Ted will want to sense longer = period=20 quakes which are a small fraction of this amplitude and to filter them = out, so=20 he needs the background to be at least 100 counts. =20

      =20 Regards,

       Chris = Chapman=20
Subject: Questions From: Roger Sparks rsparks@.......... Date: Wed, 18 Oct 2006 08:30:43 -0700 Hi Ted, Congratulations on making your new seismometer operational. Welcome to the hobby. psn-l-digest-request@.............. wrote: > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 1 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Questions > From: "tchannel" > Date: Tue, 17 Oct 2006 12:30:51 -0600 > > This is a multi-part message in MIME format. > > ------=_NextPart_000_0003_01C6F1E8.14FC65F0 > Content-Type: text/plain; > charset="iso-8859-1" > Content-Transfer-Encoding: quoted-printable > > I have finished my sensor, and have had it running for three days. > > 1. During the night hours, 11pm to 6am, the tract goes from normal to = > noisy, getting worse each hour. The sensor sits in the garage on a = > concrete slab. No draft and no heat. As soon as I go into the garage = > in the AM and the room gets warmer, because the sun warms the room to = > about 60 f. The trace returns to normal. Is this temperature effect? I = > also turn off the monitor and turn it back on in the AM. Could the CTR = > or the computer create noise? They set about three feet from the sensor. = > Again no heat, no draft and nothing running out there in the night. > You do not mention a cover over the seismometer. A garage provides a cover which is much too large to prevent internal heat driven air currents which a seismometer will easily detect. Try a much smaller cover over the seismometer. The Plexiglas cover you are considering should be adequate, but you may also need some heating as suggested by Chris. The heating should be less to control air currents, but would work more to stabilize heat related dimensional changes to the seismometer components. > 2. I think I am getting a good recording, I have see the last two = > quakes and to me they look normal. > I am in Boise Idaho and have tried to compare my .PSN with any others = > close by. However our local one in Boise is down and the next, nearest = > one is in Washington State. Now here is a hard question to ask: I = > created my expanded trace, using the same time plotted on the .PSN in = > Washington (061017.013725.ebgz.psn M6.5 10356km from Ellensburg, Wa.,) = > This was around one hour of trace. I did this so I could compare the = > two side by side. I was a little surprised to see the Wa. psn to show a = > large spike on the P and a short spike on the S. My trace looks very = > similar, but I show a large spike on the S and a smaller spike on the P. = > From the description of the Ellensburg Wa file it has a Z in it, is = > that a Vertical sensor? and since my sensor is a Horz pointing N/S, = > would that explain the different. These events came from the East, and I = > have my beam pointing North. > Anyone who would like me to send both .PSN's to them for a critique, = > please email me. I would appreciate someone looking at them and = > voicing an opinion as to my level of gain, not sure if it is correct, = > and some advise as to how to best filter this event to enhance the P and = > S. I am just using trial and error. > Please post your files to the PSN web site. The seismometer at ebgz is mostly vertical but has a tilt of about 20 degrees above horizontal and runs north/south. The best filter to use depends upon the quake so trial and error is the rule. You will see quakes originating in Idaho or Montana much better if you use a high pass filter, passing frequencies of about 0.5 Hz and higher. These local quakes will have frequencies present up to about 10 Hz. Station ebgz http://www.seismicnet.com/quakes/0610/061014.153020.ebgzx.psn demonstrates the effectiveness of a high pass filter on local quake data. > 3. Presently I am building a Plexiglas box. But would it help to = > reduce noise if I built a second box wrapped with alum foil? Or other = > ideas on building a box which would make a positive different? > > 4. I know weather can alter the way the trace looks, I thought my = > situation was weather, but it was clear today. > What is there in a front moving thru that creates the noise? Lets say = > a front with little wind and no lightening. > > Many thanks, Ted > Best wishes, Roger __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Questions From: "Benji Johnson" Benji.Johnson@.................. Date: Wed, 18 Oct 2006 12:56:55 -0700 Hi Ted, I don't know how much practical difference this makes, but in addition to placing an insulated cover over the sensor, I also place 1/4" of the rigid foam insulation on the concrete floor, in order to further insulate it from temperature changes. This extends 6 - 8" beyond the outer edge of the box. If you place your sensor onto this foam, the feet will leave an imprint, which you then need to cut out slightly oversized with a knife so that there is contact with the floor. If the legs on your sensor are longer, you could go with thicker insulation, but you don't want there to be any contact with this insulation. Lastlly, I attach a soft "garage door" insulation strip onto the floor insulation, which the box then sits upon. This seems to provide a nice seal against air leaks between the two hard insulation surfaces. In the past, others have mentioned filling some of the empty space within the cover with light foam, so as to displace air which might otherwise cause problems if it becomes convective. On the other hand, I could see this being a problem if all that you end up doing is focusing the remaining air movement onto the coil. Again, I'm not sure that either of these additional steps make a real difference, but thought I'd throw them out as food for thought. Benji __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Questions From: "Jack Ivey" ivey@.......... Date: Wed, 18 Oct 2006 16:29:24 -0400 Also, even with the cover, you might end up with convection currents within the box, due to the concrete staying warm while the air above cools at night. Some people put a small (10 watt?) heater or light bulb inside the top of the box, causing the air at in the box to stratify. The idea is to make sure each layer=20 of air is warmer than the one below it to eliminate convection currents. Jack -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Benji Johnson Sent: Wednesday, October 18, 2006 3:57 PM To: PSN-L@.............. Subject: Re: Questions Hi Ted, I don't know how much practical difference this makes, but in addition to placing an insulated cover over the sensor, I also place 1/4" of the rigid foam insulation on the concrete floor, in order to further insulate it from temperature changes. This extends 6 - 8" beyond the outer edge of the box. If you place your sensor onto this foam, the feet will leave an imprint, which you then need to cut out slightly oversized with a knife so that there is contact with the floor. If the legs on your sensor are longer, you could go with thicker insulation, but you don't want there to be any contact with this insulation.=20 Lastlly, I attach a soft "garage door" insulation strip onto the floor insulation, which the box then sits upon. This seems to provide a nice seal against air leaks between the two hard insulation surfaces. In the past, others have mentioned filling some of the empty space within the cover with light foam, so as to displace air which might otherwise cause problems if it becomes convective. On the other hand, I could see this being a problem if all that you end up doing is focusing the remaining air movement onto the coil. Again, I'm not sure that either of these additional steps make a real difference, but thought I'd throw them out as food for thought. Benji __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Question about expected performance From: Larry Conklin lconklin@............ Date: Wed, 18 Oct 2006 16:40:17 -0400 Hi Ted, I have been running a Shakelford-Gunderson sensor since mid 2000, and in that time have collected a little over 500 events. I made up a couple of Excel spreadsheets to keep track of them. The spreadsheets automatically plot the events on a magnitude - distance scatter plot along with a color coded (and very subjective) measure of "quality" of the detection. At my location in central NY my plots show a lot of detections from about Mag 5.5 and up at ranges of 3000 mi and greater. Closer in than 3000 mi, I see a lot of stuff at lower magnitudes. I think the noise performance of my set-up leaves a lot to be desired but that otherwise, it seems to do about as well as people are reporting for their Lehmans. I could send you copies of my data if you're interested. I think this listserve strips off attachments, but I will send the info directly to anyone who is curious. Larry Conklin lconklin@............ tchannel wrote: > > Q 2. What are the expectations of a Lehman sensor? I know that depends > on many factors, and not the lease of which is the quality of the > sensor, and its environment, as well as the type and location of the > events. But just in general terms. The AS1, which is not a Lehman > suggest one should be able to see 6.0m from several thousand mile away, > or something like that. > The reason I ask, I do hear statements, both over and under my > expectations. Time will tell, but I wanted your opinions. > > Cheers, Ted __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Questions From: ChrisAtUpw@....... Date: Wed, 18 Oct 2006 16:48:38 EDT In a message dated 2006/10/18, tchannel@.............. writes: > As a newcomer to these issues, I had no idea the importance of these > enclosures. I did not realize that invisible air currents in the room, caused by > the different in floor vs. air temperature, would cause huge noise. Hi Ted, With Larry's low noise amplifier and a Neo magnet sensor, your amplifier noise level is likely as a rough guess to be less than 20 nano metres. That is 20 millionths of 1 mm. My Lehman LVDT sensor has a noise level of about 7 nano metres, but the environmental noise is well over 10x this. These sensors are extremely sensitive. > Q 1. I understand that some people orient their sensor N/S others E/W, Are > the sensors ever oriented at a 45 degree angle between the two? It is entirely up to you, but if you want to compare your results with others, or with USGS sites, you need the same orientation. Remember that if the axis of the Lehman is N/S, the detection sensitivity is E/W. > Q 2. What are the expectations of a Lehman sensor? I know that depends on > many factors, and not the lease of which is the quality of the sensor, and its > environment, as well as the type and location of the events. But just in > general terms. The AS1, which is not a Lehman suggest one should be able to see > 6.0m from several thousand mile away, or something like that. You should be able to get significantly better results than an AS-1, but what you see is likely to depend almost entirely on the local man made and natural environmental noise. With say a 25 to 30 sec period, good bearings and a rigid frame, I would expect you to be able to detect mag 6 quakes world wide. Mag 3 quakes from 200 to maybe 500 km. You need to learn how best to set your display filters. The professionals can get better results since they choose low noise sites and may also bury their seismometers ~100 m deep to reduce surface noise. See http://jclahr.com/science/psn/magnitude.html Note the small control buttons at the bottom of the screen. Regards, Chris Chapman In a me= ssage dated 2006/10/18, tchannel@.............. writes:

As a newcomer to these issues,=20= I had no idea the importance of these enclosures.   I did not real= ize that invisible air currents in the room, caused by the different in floo= r vs. air temperature, would cause huge noise.


Hi Ted,
      
       With Larry's low noise amplifier and a=20= Neo magnet sensor, your amplifier noise level is likely as a rough guess to=20= be less than 20 nano metres. That is 20 millionths of 1 mm. My Lehman LVDT s= ensor has a noise level of about 7 nano metres, but the environmental noise=20= is well over 10x this. These sensors are extremely sensitive.

Q 1. I understand that some pe= ople orient their sensor N/S others E/W,  Are the sensors ever oriented= at a 45 degree angle between the two?


       It is entirely up to you, but if you w= ant to compare your results with others, or with USGS sites, you need the sa= me orientation. Remember that if the axis of the Lehman is N/S, the detectio= n sensitivity is E/W.

Q 2. What are the expectations= of a Lehman sensor? I know that depends on many factors, and not the lease=20= of which is the quality of the sensor, and its environment, as well as the t= ype and location of the events. But just in general terms. The AS1, which is= not a Lehman suggest one should be able to see 6.0m from several thousand m= ile away, or something like that. 


       You should be able to get significantly= better results than an AS-1, but what you see is likely to depend almost en= tirely on the local man made and natural environmental noise. With say a 25=20= to 30 sec period, good bearings and a rigid frame, I would expect you to be=20= able to detect mag 6 quakes world wide. Mag 3 quakes from 200 to maybe 500 k= m. You need to learn how best to set your display filters. The professionals= can get better results since they choose low noise sites and may also bury=20= their seismometers ~100 m deep to reduce surface noise.

       See http://jclahr.com/science/psn/magni= tude.html Note the small control buttons at the bottom of the screen.

       Regards,

       Chris Chapman Subject: Re: Long period sensor plan From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Wed, 18 Oct 2006 23:44:18 +0000 Hi Here is a updated drawing of the sensor, http://www.simnet.is/jonfr500/sensor/long.period.sensor.v1.0.1.jpg This sensor is based on mass. It won't have any springs in it. But a damping system on the end and a magnets and coils in front of it. I am also going to use a resistance to get the signal as close to 1Hz as I can. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Questions From: Barry Lotz barry_lotz@............. Date: Wed, 18 Oct 2006 20:07:26 -0700 (PDT) Hi Ted It seems that we all have the issue of how sensitive to make the system. More sensitive and you can pick up more distant events but if it is too sensitive one gets clipped signals during stronger events. Larry's circuits and others have two recording gain levels which is probably the best but one could set the gain lower and use a higher bit A/D converter like 24 bit. I have plotted magnitude vs distance vs count for my systems and have selected some level which is ok with me for the time being but like any hobby, there is always a desire to improve. Regards Barry snip- Q 2. What are the expectations of a Lehman sensor? I know that depends on many factors, and not the lease of which is the quality of the sensor, and its environment, as well as the type and location of the events. But just in general terms. The AS1, which is not a Lehman suggest one should be able to see 6.0m from several thousand mile away, or something like that. The reason I ask, I do hear statements, both over and under my expectations. Time will tell, but I wanted your opinions. Cheers, Ted
Hi Ted
  It seems that we all have the issue of how sensitive to make the system. More sensitive and you can pick up more distant events but if it is too sensitive one gets clipped signals during stronger events. Larry's circuits and others have two recording gain levels which is probably the best but one could set the gain lower and use a higher bit A/D converter like 24 bit. I have plotted magnitude vs distance vs count for my systems and have selected some level which is ok with me for the time being but like any hobby, there is always a desire to improve.
Regards
Barry
 

snip-
 
Q 2. What are the expectations of a Lehman sensor?  I know that depends on many factors, and not the lease of which is the quality of the sensor, and its environment, as well as the type and location of the events.  But just in general terms. The AS1, which is not a Lehman suggest one should be able to see 6.0m from several thousand mile away, or something like that.
The reason I ask, I do hear statements, both over and under my expectations.  Time will tell, but I wanted your opinions.
 
Cheers, Ted
 
Subject: Re: Questions From: ian ian@........... Date: Thu, 19 Oct 2006 06:47:47 +0100 I connect my sensor to 3 channels of my 16 bit A/D, each of which are set to differrent gains/maximum input voltage. In realtime, the software uses the highest gain channel that isn't saturated for each sample. This, in some respects, gets about 21 bits of resolution out of my 16 bit A/D. Obviously the voltage resolution of the signal deminishes as it moves up the channels but it avoids saturation and you don't need the highest voltage resolution as the signal increases in magnitude. Ian Barry Lotz wrote: > Hi Ted > It seems that we all have the issue of how sensitive to make the > system. More sensitive and you can pick up more distant events but if > it is too sensitive one gets clipped signals during stronger events. > Larry's circuits and others have two recording gain levels which is > probably the best but one could set the gain lower and use a higher > bit A/D converter like 24 bit. I have plotted magnitude vs distance vs > count for my systems and have selected some level which is ok with me > for the time being but like any hobby, there is always a desire to > improve. > Regards > Barry > > > snip- > > Q 2. What are the expectations of a Lehman sensor? I know that > depends on many factors, and not the lease of which is the quality > of the sensor, and its environment, as well as the type and > location of the events. But just in general terms. The AS1, which > is not a Lehman suggest one should be able to see 6.0m from > several thousand mile away, or something like that. > The reason I ask, I do hear statements, both over and under my > expectations. Time will tell, but I wanted your opinions. > > Cheers, Ted > > I connect my sensor to 3 channels of my 16 bit A/D, each of which are set to differrent gains/maximum input voltage.  In realtime, the software uses the highest gain channel that isn't saturated for each sample.  This, in some respects, gets about 21 bits of resolution out of my 16 bit A/D.  Obviously the voltage resolution of the signal deminishes as it moves up the channels but it avoids saturation and you don't need the highest voltage resolution as the signal increases in magnitude.

Ian

Barry Lotz wrote:
Hi Ted
  It seems that we all have the issue of how sensitive to make the system. More sensitive and you can pick up more distant events but if it is too sensitive one gets clipped signals during stronger events. Larry's circuits and others have two recording gain levels which is probably the best but one could set the gain lower and use a higher bit A/D converter like 24 bit. I have plotted magnitude vs distance vs count for my systems and have selected some level which is ok with me for the time being but like any hobby, there is always a desire to improve.
Regards
Barry
 

snip-
 
Q 2. What are the expectations of a Lehman sensor?  I know that depends on many factors, and not the lease of which is the quality of the sensor, and its environment, as well as the type and location of the events.  But just in general terms. The AS1, which is not a Lehman suggest one should be able to see 6.0m from several thousand mile away, or something like that.
The reason I ask, I do hear statements, both over and under my expectations.  Time will tell, but I wanted your opinions.
 
Cheers, Ted
 

Subject: Redwood City PSN Website Is Down From: Larry Cochrane lcochrane@.............. Date: Thu, 19 Oct 2006 22:14:36 -0700 Hi Tony and other PSNers, I'm having a DSL outage. Luckily I have two DSL line just for this type of problem, so I'm not totally off-line. Hopefully www.seismicnet.com will be back on the air in a few days. My web site can be accessed using this domain name psn.seismicnet.com or psn.quake.net. Email should be working just fine. Regards, Larry Cochrane Redwood City, PSN quakekona wrote: > Hi Larry. > > I just wanted you to know, if you didn't already, that your www.seismicnet.com > website is down. It wont open for me, however psn.quake.net is working. > Just to remind you, I will be shutting down SDR on saturday for 2 weeks. > I hope you have enjoyed all the aftershocks, I just posted 3 more today, but > there won't be anymore postings after saturday until I get back...sorry. > Until I talk to you again... > > Aloha > > Tony > > > > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Two Ca. Events From: "tchannel" tchannel@.............. Date: Fri, 20 Oct 2006 14:31:07 -0600 Hi Folks, I just recorded the 4.5m from Northern Cal. When I placed = the p and s there was a strong single 4 mins in front of it. I when back to the maps and found a 1.5m in the same general area. Both = singles were clear and pronounced. The time seems exactly correct for = the 1.5 as well as the 4.5. Could I have seen a 1.5m 472miles away, = here in Boise? Happy to send the .psn if that would help. Thanks Ted
Hi Folks,   I just recorded = the 4.5m from=20 Northern Cal.  When I placed the p and s there was a strong single = 4 mins=20 in front of it.
I when back to the maps and found a = 1.5m in the=20 same general area.  Both singles were clear and pronounced.  = The time=20 seems exactly correct for the 1.5 as well as the 4.5.  Could I have = seen a=20 1.5m 472miles away, here in Boise?
Happy to send the .psn if that would=20 help.
Thanks Ted
Subject: Re: Two Ca. Events From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Fri, 20 Oct 2006 21:09:31 +0000 Hi Don't expect to see mag 1.5 at ~700 km distance, I can see them up to ~150 km away from me. But send me the psn file so I can take a look. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Two Ca. Events From: ChrisAtUpw@....... Date: Fri, 20 Oct 2006 22:46:48 EDT In a message dated 2006/10/20, tchannel@.............. writes: > Hi Folks, I just recorded the 4.5m from Northern Cal. When I placed the > p and s there was a strong single 4 mins in front of it. > I when back to the maps and found a 1.5m in the same general area. Hi Ted, First check your filtering. You won't see a M1.5 from 472 m. I suggest that you check the lists again later today / tomorrow. www.iris.edu/seismon is now showing a M4.5 at 17:00:06 in N CA Regards, Chris Chapman In a me= ssage dated 2006/10/20, tchannel@.............. writes:

Hi Folks,   I just re= corded the 4.5m from Northern Cal.  When I placed the p and s there was= a strong single 4 mins in front of it.
I when back to the maps and found a 1.5m in the same general area. <= FONT COLOR=3D"#000000" BACK=3D"#ffffff" style=3D"BACKGROUND-COLOR: #ffffff"= SIZE=3D3 PTSIZE=3D12 FAMILY=3D"SANSSERIF" FACE=3D"Arial" LANG=3D"0">

Hi Ted,

       First check your filtering. You won't s= ee a M1.5 from 472 m.
       I suggest that you check the lists agai= n later today / tomorrow. 

       www.iris.edu/seismon is now showing a M= 4.5 at 17:00:06 in N CA

       Regards,

       Chris Chapman Subject: Local vs distance events From: "tchannel" tchannel@.............. Date: Mon, 23 Oct 2006 08:48:37 -0600 Hi, I was asked to explain the different between Sensors developed for = local events vs those developed for long distance events. Is there a summary posted that explains this in terms easy to = understand? This is for a group of children and adults. Thanks, Ted
Hi,  I was asked to explain the = different=20 between Sensors  developed for local events vs those developed = for=20 long distance events.
Is there a summary posted that explains = this in=20 terms easy to understand?   This is for a group of children = and=20 adults.
Thanks, Ted
Subject: Re: Local vs distance events From: John or Jan Lahr JohnJan@........ Date: Mon, 23 Oct 2006 08:45:28 -0700 At 07:48 AM 10/23/2006, you wrote: >Hi, I was asked to explain the different between Sensors developed >for local events vs those developed for long distance events. >Is there a summary posted that explains this in terms easy to >understand? This is for a group of children and adults. >Thanks, Ted Hi Ted, Local earthquakes are rich in all frequencies. The best frequencies for picking sharp arrival times for P, S and other phases are the high frequencies, above 1 Hz. As the waves from an earthquake travel away from the source, the higher frequencies are attenuated more quickly than the low frequencies. At a great distance most of the energy is at frequencies lower than 1 Hz. In particular, surface waves with frequencies of 1/20 Hz (20 second period) usually are the most prominent signal for very distant events (call teleseisms). The other factor for consideration is the frequency of the "noise" in the earth. There is a peak in this noise at a period of 4 to 5 seconds. This is due to what are called higher-mode surface waves from non-earthquake sources such as wind and ocean storms. Look a the graph on this site to see a plot of the background noise: http://dmc.iris.washington.edu/stations/seisWorkshop04/iris_sensor_ws_9.19.05.pdf In the days of paper seismograms, two different systems were generally used: a short-period system for frequencies higher than 1 Hz and a long period system with peak response near 1/15 Hz (15 second period). See: . With the advent of digital recording, many new systems are "broad band," meaning that they are sensitive to a wide range of frequencies. In order to view data from one of these systems it is often best to use a digital filter to create either a short period or a long period seismogram. This graph shows the growth of broad-band stations and the decline of the older worldwide photograph-paper systems from the WWSSN ( World-Wide Standard Seismograph Network). The response of the broad-band station at Corvallis, Oregon (COR) is shown on this page: . On this page one can toggle between the broad-band seismogram and one that is filtered to become either a short period or a long period seismogram. Very distant events are usually not even visible on the short-period seismogram, where as a local or regional event will be seen best on the short-period record. Hope this helps! I've included a lot of details so that you will have to background necessary to develop a simpler explanation. Cheers, John __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Local vs distance events From: ChrisAtUpw@....... Date: Mon, 23 Oct 2006 11:56:40 EDT In a message dated 2006/10/23, tchannel@.............. writes: > Hi, I was asked to explain the different between Sensors developed for > local events vs those developed for long distance events. > Is there a summary posted that explains this in terms easy to understand? > This is for a group of children and adults. Hi Ted, ????? Are these amateur or professional sensors? There are a variety of sensors available professionally. 4.5 Hz and more particularly 1 Hz geophones may be used for local quakes / volcanoes and may record from 60 Hz down to the corner frequency. Then you have a variety of broad band medium to high sensitivity seismic sensors which record from 50 / 40 Hz all the way to 40, 60, 120 or even 360 seconds. Then there are 'strong motion' sensors, more often used close to faults or for civil engineering. These record accelerations up to about 2 g but may only go down to a milli g and are usually broad band. Local events may have motion components from maybe 40 Hz down to 30 seconds. As quake waves travel through / over the surface of the Earth, the higher frequencies are selectively absorbed. Teleseismic quakes tend to have P waves of 1 to 2 Hz, S waves about 0.45 the frequency of the P waves and Love / Rayleigh long surface waves with periods less than 60 seconds, often about 15 to 30 seconds. However, those from 'great' quakes may have waves of much greater periods. Regards, Chris Chapman In a me= ssage dated 2006/10/23, tchannel@.............. writes:

Hi,  I was asked to explai= n the different between Sensors developed for local events vs those develope= d for long distance events.
Is there a summary posted that explains this in terms easy to understand? T= his is for a group of children and adults.


Hi Ted,

       ?????

       Are these amateur or professional senso= rs?

       There are a variety of sensors availabl= e professionally.
       4.5 Hz and more particularly 1 Hz geoph= ones may be used for local quakes / volcanoes and may record from 60 Hz down= to the corner frequency.
       Then you have a variety of broad band m= edium to high sensitivity seismic sensors which record from 50 / 40 Hz all t= he way to 40, 60, 120 or even 360 seconds.
       Then there are 'strong motion' sensors,= more often used close to faults or for civil engineering. These record acce= lerations up to about 2 g but may only go down to a milli g and are usually=20= broad band.

       Local events may have motion components= from maybe 40 Hz down to 30 seconds.

       As quake waves travel through / over th= e surface of the Earth, the higher frequencies are selectively absorbed.

       Teleseismic quakes tend to have P waves= of 1 to 2 Hz, S waves about 0.45 the frequency of the P waves and Love / Ra= yleigh long surface waves with periods less than 60 seconds, often about 15=20= to 30 seconds. However, those from 'great' quakes may have waves of much gre= ater periods.

       Regards,

       Chris Chapman Subject: Re: Local vs distance events From: "tchannel" tchannel@.............. Date: Mon, 23 Oct 2006 16:07:18 -0600 Thanks for this information. Chris, These are amateur sensors, and = students. Ted ----- Original Message -----=20 From: ChrisAtUpw@.......... To: psn-l@................. Sent: Monday, October 23, 2006 9:56 AM Subject: Re: Local vs distance events In a message dated 2006/10/23, tchannel@.............. writes: Hi, I was asked to explain the different between Sensors developed = for local events vs those developed for long distance events. Is there a summary posted that explains this in terms easy to = understand? This is for a group of children and adults. Hi Ted,=20 ????? Are these amateur or professional sensors? There are a variety of sensors available professionally.=20 4.5 Hz and more particularly 1 Hz geophones may be used for = local quakes / volcanoes and may record from 60 Hz down to the corner = frequency. Then you have a variety of broad band medium to high = sensitivity seismic sensors which record from 50 / 40 Hz all the way to = 40, 60, 120 or even 360 seconds. Then there are 'strong motion' sensors, more often used close = to faults or for civil engineering. These record accelerations up to = about 2 g but may only go down to a milli g and are usually broad band. Local events may have motion components from maybe 40 Hz down = to 30 seconds. As quake waves travel through / over the surface of the Earth, = the higher frequencies are selectively absorbed. Teleseismic quakes tend to have P waves of 1 to 2 Hz, S waves = about 0.45 the frequency of the P waves and Love / Rayleigh long surface = waves with periods less than 60 seconds, often about 15 to 30 seconds. = However, those from 'great' quakes may have waves of much greater = periods. Regards, Chris Chapman
Thanks for this = information.  =20 Chris, These are  amateur sensors, and students.  =20 Ted
----- Original Message -----
From:=20 ChrisAtUpw@.......
Sent: Monday, October 23, 2006 = 9:56=20 AM
Subject: Re: Local vs distance=20 events

In a=20 message dated 2006/10/23, tchannel@..............=20 writes:

Hi,  I was asked to explain the different between = Sensors=20 developed for local events vs those developed for long distance=20 events.
Is there a summary posted that explains this in = terms easy to=20 understand? This is for a group of children and = adults.


Hi=20 Ted,

      =20 ?????

       Are these amateur or = professional sensors?

       = There are a=20 variety of sensors available professionally.=20
       4.5 Hz and more particularly = 1 Hz=20 geophones may be used for local quakes / volcanoes and may record from = 60 Hz=20 down to the corner frequency.
       = Then you=20 have a variety of broad band medium to high sensitivity seismic = sensors which=20 record from 50 / 40 Hz all the way to 40, 60, 120 or even 360=20 seconds.
       Then there are = 'strong=20 motion' sensors, more often used close to faults or for civil = engineering.=20 These record accelerations up to about 2 g but may only go down to a = milli g=20 and are usually broad = band.

       Local=20 events may have motion components from maybe 40 Hz down to 30=20 seconds.

       As quake waves = travel=20 through / over the surface of the Earth, the higher frequencies are=20 selectively absorbed.

       = Teleseismic=20 quakes tend to have P waves of 1 to 2 Hz, S waves about 0.45 the = frequency of=20 the P waves and Love / Rayleigh long surface waves with periods less = than 60=20 seconds, often about 15 to 30 seconds. However, those from 'great' = quakes may=20 have waves of much greater=20 periods.

      =20 Regards,

       Chris = Chapman=20
Subject: Unkown teleseimic signal From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Mon, 23 Oct 2006 23:03:34 +0000 Hi all I did notice a unkown teleseismic singal on few of the helcorders that I montior. None of the known earthquakes fit within the the appearance of that signal, the latest big earthquake was at 21:17 UTC and that was a mag 6.1 earthquake in Japan reagion. So far nothing has appeard on emsc-csem or usgs that explains the timeing of that signal. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Unkown teleseimic signal From: "Geoffrey" gmvoeth@........... Date: Mon, 23 Oct 2006 16:43:10 -0700 Mr. Jón Frímann; When you talk about any unknown signals, can you please tell the UTC date and time and position at which the unknown signal was received. Most unknown I have received have turned out to be mining operations. These will usually be within 150 Statute miles from me. They will normally happen during daylight weekdays and between the hours of 1400 and 1700 locally. They look like small regional quakes between 2 and 3.5 in Richter magnitude. Or so I am led to believe. I have two (L or S)-P times that are dead givaways they are like 7 seconds or 25 seconds. Regards; geoff ----- Original Message ----- From: "Jón Frímann" To: "PSN-Postlist" Sent: Monday, October 23, 2006 4:03 PM Subject: Unkown teleseimic signal > Hi all > > I did notice a unkown teleseismic singal on few of the helcorders that I > montior. None of the known earthquakes fit within the the appearance of > that signal, the latest big earthquake was at 21:17 UTC and that was a > mag 6.1 earthquake in Japan reagion. So far nothing has appeard on > emsc-csem or usgs that explains the timeing of that signal. > > Regards. > -- > Jón Frímann > http://www.jonfr.com > http://www.simnet.is/jonfr500/earthquake/ > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Unkown teleseimic signal From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Tue, 24 Oct 2006 00:17:23 +0000 Hi This signal did appear on few of the helcorders in monitor on my own webpage. It didn't appear on my sensor (far as I know). The signal appears around 22:07 UTC, on the 23rd October, 2006. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Dissipation of Seismic Waves From: "Bob Hancock" carpediem1@......... Date: Mon, 23 Oct 2006 18:14:40 -0700 Hi All - I believe that the intensity of light drops by the square of the distance i.e., double the distance and the new value is the square root of the distance. How does this apply to seismic waves which are basically sound waves? In addition, how does this affect the amplitude and radiated seismic energy of the waves? Bob Hancock

Hi All -

 

I believe that the intensity of light drops by the square of the distance = i.e., double the distance and the new value is the square root of the = distance.  How does this apply to seismic waves which are basically sound = waves?  In addition, how does this affect the amplitude and radiated seismic energy = of the waves? 

 

Bob Hancock

Subject: Earthtides From: Bill S wls@......... Date: Tue, 24 Oct 2006 12:38:54 -0400 Hi, Does anyone know of a site showing live earthtide measurements? Bill S __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Earthtides From: ian ian@........... Date: Tue, 24 Oct 2006 17:44:18 +0100 Hi, I'm not sure if you mean ocean waves. If so: https://www.fnmoc.navy.mil/PUBLIC/WAM/all_glbl.html Bill S wrote: > Hi, > Does anyone know of a site showing live earthtide measurements? > Bill S > > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of > the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Earthtides From: Bill S wls@......... Date: Tue, 24 Oct 2006 13:15:38 -0400 No, not ocean waves. I mean the deformation of the earth as affected by the gravity of the sun and moon. >Hi, > >I'm not sure if you mean ocean waves. If so: >https://www.fnmoc.navy.mil/PUBLIC/WAM/all_glbl.html > >Bill S wrote: > >>Hi, >>Does anyone know of a site showing live earthtide measurements? >>Bill S >> >> >>__________________________________________________________ >> >>Public Seismic Network Mailing List (PSN-L) >> >>To leave this list email PSN-L-REQUEST@.............. with the body of >>the message (first line only): unsubscribe >>See http://www.seismicnet.com/maillist.html for more information. >> > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with the body of the >message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Earthtides From: ChrisAtUpw@....... Date: Tue, 24 Oct 2006 13:23:09 EDT In a message dated 2006/10/24, wls@......... writes: Does anyone know of a site showing live earthtide measurements? > Bill S Hi Bill, They are measured by the ECGS at Walferdange in Belgium, but I don't know what is 'on-line'. See http://www.ecgs.lu/index.php?Itemid=1 Nicolas d'Oreye is very helpful. There are biaxial tiltmeters near Seattle in Washington State. See http://cires.colorado.edu/~bilham/ They say that data from the Long Caldera Valley is available subject to power outages.... Regards, Chris Chapman In a me= ssage dated 2006/10/24, wls@......... writes:

Does anyone know of a site showing live earthtide measurements?
Bill S



Hi Bill,

       They are measured by the ECGS at Walfer= dange in Belgium, but I don't know what is 'on-line'.
       See http://www.ecgs.lu/index.php?Itemid= =3D1
       Nicolas d'Oreye is very helpful.

       There are biaxial tiltmeters near Seatt= le in Washington State. See http://cires.colorado.edu/~bilham/
       They say that data from the Long Calder= a Valley is available subject to power outages....

       Regards,

       Chris Chapman Subject: Re: Earthtides From: Stephen & Kathy skmort@............ Date: Tue, 24 Oct 2006 10:54:54 -0700 I think this is what your looking for: http://aiuas3.unibe.ch/dpgm/zm_graph_tide.html Stephen PSN Station #55 Bill S wrote: > Hi, > Does anyone know of a site showing live earthtide measurements? > Bill S > > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of > the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > I think this is what your looking for:

http://aiuas3.unibe.ch/dpgm/zm_graph_tide.html

  Stephen
  PSN Station #55

Bill S wrote:
Hi,
Does anyone know of a site showing live earthtide measurements?
Bill S


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Subject: Re: Dissipation of Seismic Waves From: "Geoffrey" gmvoeth@........... Date: Tue, 24 Oct 2006 12:37:00 -0700 Spreading losses are the square of the distance so long as the spreading is 3D. There are other losses also. Several in fact. But it boils down to the generation of heat which is lost to entropy forever. It was so long ago that I studied this in SONAR and can no longer remember everything. Regards; geoff ----- Original Message ----- From: "Bob Hancock" To: "'PSN'" Sent: Monday, October 23, 2006 6:14 PM Subject: Dissipation of Seismic Waves > Hi All - > > > > I believe that the intensity of light drops by the square of the distance > i.e., double the distance and the new value is the square root of the > distance. How does this apply to seismic waves which are basically sound > waves? In addition, how does this affect the amplitude and radiated seismic > energy of the waves? > > > > Bob Hancock > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: My seismometer vault solution From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Wed, 25 Oct 2006 00:30:38 +0000 Hi all I have finally figured out a good way to put my geophone underground, into relative quite and noise free envroment (as can be done here). I am going to have put it in a plast bucket with a waterproof top. That is the only cheap way for me to do it, I have looked at other options and they are exspensive for me and hard to impliment, since this solution has to be waterproof and that is the most important factor in all of this. I plan to put my geophone underground soon as possible, problay next week. Becose I have to do it before the ground completie freezes over. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: My seismometer vault solution From: ian ian@........... Date: Wed, 25 Oct 2006 07:23:03 +0100 Hi, you can also use plastic soil pipe (the piping used for toilets and is about 5" in diameter). You'll find lots of different parts to put together in the plumbing shops. You can glue them together and drill a hole for the geophone metal spike to stick out of. Cheers Ian Jón Frímann wrote: >Hi all > >I have finally figured out a good way to put my geophone underground, >into relative quite and noise free envroment (as can be done here). I am >going to have put it in a plast bucket with a waterproof top. That is >the only cheap way for me to do it, I have looked at other options and >they are exspensive for me and hard to impliment, since this solution >has to be waterproof and that is the most important factor in all of >this. I plan to put my geophone underground soon as possible, problay >next week. Becose I have to do it before the ground completie freezes >over. > >Regards. > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Dissipation of Seismic Waves From: John or Jan Lahr JohnJan@........ Date: Tue, 24 Oct 2006 23:49:40 -0700 At 06:14 PM 10/23/2006, you wrote: >Hi All - > >I believe that the intensity of light drops by the square of the >distance i.e., double the distance and the new value is the square >root of the distance. How does this apply to seismic waves which >are basically sound waves? In addition, how does this affect the >amplitude and radiated seismic energy of the waves? > >Bob Hancock Hi Bob, The graphs on the page below of amplitude versus distance show how seismic waves decay with distance. Ground motion amplitude and velocity as a function of distance, magnitude, and depth. (Only works well with MSIE -- Not Firefox.) Keep in mind that bacteria range from about 1 to 10 microns in diameter, while a human hair may be from 50 to 100 microns in diameter. For waves that expand in three dimensions, ignoring conversion to heat, the total energy flux through a sphere at any radius will be constant. The surface area of the sphere is 4 pi r^2, so the energy per unit area must be proportional to 1/r^2. The energy carried by the wave is proportional to the amplitude squared (A^2), so A^2 is proportional to 1/r^2, or A is proportional to 1/r. I'm not sure how to relate this to the amplitude at the surface versus geocentric distance for body waves in a spherical earth with velocity that varies with depth! For surface waves that are constrained to the surface of the earth, ignoring conversion to heat or leaking of some energy into the interior, the total energy flux through a circular zone or any radius will be constant. The area of the outer edge of a circular zone of a given thickness is proportional to the radius of the zone, so the energy per unit area must be proportional to 1/r. Then, since the energy is proportional to A^2, A^2 is proportional to 1/r, or A is proportional to 1/sqrt(r). From the formula for surface wave magnitude, Ms = log (A/T) + 1.66 log D + 3.3, one can show that the Amplitude is proportional to 1/ (D^1.66) This is much faster decay than 1/(D^.5), due, I suppose, to attenuation (conversion of energy to heat) and leaking of energy into the interior of the Earth. Actually the amplitude increases again near the opposite side of the earth as the surface waves converge from all directions. See: http://jclahr.com/science/software/magnitude/ms/msmag.html Don't know if this helps much! Cheers, John __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: My seismometer vault solution From: "Geoffrey" gmvoeth@........... Date: Wed, 25 Oct 2006 00:26:16 -0700 The air must be kept absolutely dry if you have a closed system. You need something included inside the container to absorb any free moisture. In the military they pump dry nitrogen into closed cavities. What is the coldest temp ? The airs dew point must be kept below that temp. I would use a pyrex like glass container specially built to keep a vacuum. Provide electrical isolation from the ground. It seems everything I want to do simply costs too much monies. I would need to be at a university working on a government funded project to try out all my ideas. Regards; geoff ----- Original Message ----- From: "Jón Frímann" To: "PSN-Postlist" Sent: Tuesday, October 24, 2006 5:30 PM Subject: My seismometer vault solution > Hi all > > I have finally figured out a good way to put my geophone underground, > into relative quite and noise free envroment (as can be done here). I am > going to have put it in a plast bucket with a waterproof top. That is > the only cheap way for me to do it, I have looked at other options and > they are exspensive for me and hard to impliment, since this solution > has to be waterproof and that is the most important factor in all of > this. I plan to put my geophone underground soon as possible, problay > next week. Becose I have to do it before the ground completie freezes > over. > > Regards. > -- > Jón Frímann > http://www.jonfr.com > http://www.simnet.is/jonfr500/earthquake/ > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: My seismometer vault solution From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Wed, 25 Oct 2006 12:07:47 +0000 Hi I am going to close the system inside, so the air is going to be resanable dry. However the sand I got might not be so dry, since I got it from outside and it is coverd in snow. I am going to let it dry (inside) for few days, at least until I have the weather to put my geophone underground. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: My seismometer vault solution From: "Jerry Payton" gpayton880@....... Date: Wed, 25 Oct 2006 07:17:24 -0500 Jon, The air inside your system WILL contain some amount of moisture. This moisture will "sweat" or condense with changes in outside tempratures. Unless the air is evacuated or nitrogen inserted into a sealed container, I think you may still have problems. Best Wishes, Jerry Payton ----- Original Message ----- From: Jón Frímann To: psn-l@.............. Sent: Wednesday, October 25, 2006 7:07 AM Subject: Re: My seismometer vault solution Hi I am going to close the system inside, so the air is going to be resanable dry. However the sand I got might not be so dry, since I got it from outside and it is coverd in snow. I am going to let it dry (inside) for few days, at least until I have the weather to put my geophone underground. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) To leave this list email PSN-L-REQUEST@.............. with the body of the message (first line only): unsubscribe See http://www.seismicnet.com/maillist.html for more information.
Jon,
 
The air inside your system WILL contain some amount of = moisture.  This=20 moisture will "sweat" or condense with changes in outside = tempratures. =20 Unless the air is evacuated or nitrogen inserted into a sealed = container, I=20 think you may still have problems.
 
Best Wishes,
Jerry Payton
----- Original Message -----
From:=20 J=F3n = Fr=EDmann=20
Sent: Wednesday, October 25, = 2006 7:07=20 AM
Subject: Re: My seismometer = vault=20 solution

Hi

I am going to close the system inside, so the = air is=20 going to be
resanable dry. However the sand I got might not be so = dry,=20 since I got
it from outside and it is coverd in snow. I am going to = let it=20 dry
(inside) for few days, at least until I have the weather to put = my
geophone underground.

Regards.
--
J=F3n = Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/j= onfr500/earthquake/

__________________________________________= ________________

Public=20 Seismic Network Mailing List (PSN-L)

To leave this list email = PSN-L-REQUEST@............... =20 with
the body of the message (first line only): unsubscribe
See = http://www.seismicnet.co= m/maillist.html=20 for more information.
Subject: Re: My seismometer vault solution From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Wed, 25 Oct 2006 12:42:36 +0000 Hi I plan to use a woll (that they use in walls here in Iceland) to minizie that, at least I hope it is going to do that. But the geophone is going to be on at least 80 cm depth, I don't know about tempature changes on that depth. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: My seismometer vault solution From: "Jack Ivey" ivey@.......... Date: Wed, 25 Oct 2006 08:44:53 -0400 Jon, You can get dessicant packs to put in your container. They contain = silica gel, absorbent clay, or alumina, or some combination. Sand isn't going to get dry soon by sitting around = your house, and you will get=20 condensation or frost if you don't put something in to soak up the = humidity. =20 =20 You can also take some wallboard (gypsum construction material used for = inside walls in houses),=20 get rid of the paper coating, and bake the inside stuff (mostly calcium = sulphate). It takes a lot of this=20 compared to other materials. =20 =20 If you are brave, quicklime (not slaked lime) also works, but unlike the = other options, it is=20 not practical to bake the water out for reuse. =20 Jack =20 ________________________________ From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Jerry Payton Sent: Wednesday, October 25, 2006 8:17 AM To: psn-l@.............. Subject: Re: My seismometer vault solution =20 Jon, =20 The air inside your system WILL contain some amount of moisture. This = moisture will "sweat" or condense with changes in outside tempratures. = Unless the air is evacuated or nitrogen inserted into a sealed = container, I think you may still have problems. =20 Best Wishes, Jerry Payton ----- Original Message -----=20 From: J=F3n Fr=EDmann =20 To: psn-l@................. Sent: Wednesday, October 25, 2006 7:07 AM Subject: Re: My seismometer vault solution =20 Hi =09 I am going to close the system inside, so the air is going to be resanable dry. However the sand I got might not be so dry, since I got it from outside and it is coverd in snow. I am going to let it dry (inside) for few days, at least until I have the weather to put my geophone underground. =09 Regards. --=20 J=F3n Fr=EDmann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ =09 __________________________________________________________ =09 Public Seismic Network Mailing List (PSN-L) =09 To leave this list email PSN-L-REQUEST@.............. with=20 the body of the message (first line only): unsubscribe See http://www.seismicnet.com/maillist.html for more information.

Jon,

You can get dessicant packs to put = in your container.=A0 They contain silica gel, absorbent clay, or alumina, = or

some combination.=A0 Sand = isn’t going to get dry soon by sitting around your house, and you will get =

condensation or frost if you = don’t put something in to soak up the humidity.=A0 =

 

You can also take some wallboard = (gypsum construction material used for inside walls in houses), =

get rid of the paper coating, and = bake the inside stuff (mostly calcium sulphate).=A0 It takes a lot of this =

compared to other materials.=A0 =

 

If you are brave, quicklime (not = slaked lime) also works, but unlike the other options, it is =

not practical to bake the water out = for reuse.

 

Jack

 

From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Jerry Payton
Sent: Wednesday, October = 25, 2006 8:17 AM
To: psn-l@..............
Subject: Re: My = seismometer vault solution

 

Jon,

 

The air inside your system WILL contain some amount of = moisture.  This moisture will "sweat" or condense with changes in outside tempratures.  Unless the air is evacuated or nitrogen inserted into = a sealed container, I think you may still have = problems.

 

Best Wishes,

Jerry Payton

----- Original Message ----- =

Sent: = Wednesday, October 25, 2006 7:07 AM

Subject: Re: My = seismometer vault solution

 

Hi

I am going to close the system inside, so the air is going to be
resanable dry. However the sand I got might not be so dry, since I = got
it from outside and it is coverd in snow. I am going to let it dry
(inside) for few days, at least until I have the weather to put my
geophone underground.

Regards.
--
J=F3n Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/j= onfr500/earthquake/

__________________________________________________________

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To leave this list email PSN-L-REQUEST@............... with
the body of the message (first line only): unsubscribe
See http://www.seismicnet.co= m/maillist.html for more information.

Subject: weather From: "tchannel" tchannel@.............. Date: Wed, 25 Oct 2006 10:16:53 -0600 Hi All, I was so happy with my sensor, over the last few day. I had a = major problem with thermos, which disappeared with my insulated box. = This question has to do with weather changes, and why that effects = noise. A day ago the tract was quiet at night and a little bit of noise during = the day time and city activities. Many hours ago a cold front came thru, arriving at 8:00 pm with winds. = The trace went from quite to noisy several hour ahead of the front. You = could look at the trace and see the change as the front got closer. = This weather should move out in the next 24 hours. So I expect things = will go back to normal. I don't understand, what is stimulating the sensor. 1. Does it respond to barometric pressure changes? 2. When wind is part of the storm, and the wind moves the trees, is = this transferred thru the ground to the sensors as earth movements? 3. Would a bolt of lightening be displayed on the trace? As a front approaches it is like the atmosphere starts to fill with = electromagnet noise. I'm just trying to understand what creates it. Inside the garage and inside the box it seem so isolated, no wind, no = air current, no vibrations or physical movements. Yet the sensor can see = a front hours before it arrives. Thanks, Ted
Hi All,   I was so happy with = my sensor,=20 over the last few day.  I had a major problem with thermos, which=20 disappeared with my insulated box.   This question has to do = with=20 weather changes, and why that effects noise.
A day ago the tract was quiet at night = and a little=20 bit of noise during the day time and city activities.
Many hours ago a cold front came = thru,=20 arriving at 8:00 pm with winds.   The trace went from quite to = noisy=20 several hour ahead of the front.  You could look at the trace and = see the=20 change as the front got closer.   This weather should move out = in the=20 next 24 hours.  So I expect things will go back to = normal.
 
I don't understand, what is stimulating = the=20 sensor.
1.  Does it respond to barometric = pressure=20 changes?
2.  When wind is part of the = storm, and the=20 wind moves the trees, is this transferred thru the ground to the sensors = as=20 earth movements?
3.  Would a bolt of lightening be = displayed on=20 the trace?
 
As a front approaches it is like the = atmosphere=20 starts to fill with electromagnet noise.  I'm just trying to = understand=20 what creates it.
Inside the garage and inside the box it = seem so=20 isolated, no wind, no air current, no vibrations or physical movements. = Yet the=20 sensor can see a front hours before it arrives.
Thanks, Ted
Subject: Re: My seismometer vault solution From: "Erich Kern" efkern@............. Date: Wed, 25 Oct 2006 09:28:43 -0700 Hi, The method I've used to dry sand is spread it on a couple of cookie tin sheets and bake in the kitchen oven at 250 F. or 120 C. for at least an hour. Let it cool on the tins before pouring into a container. Sand in a bucket will take forever to dry because the air can't get to the lower portion. There's an enormous surface area in sand that holds moisture. Erich ----- Original Message ----- From: "Jón Frímann" To: Sent: Wednesday, October 25, 2006 5:07 AM Subject: Re: My seismometer vault solution Hi I am going to close the system inside, so the air is going to be resanable dry. However the sand I got might not be so dry, since I got it from outside and it is coverd in snow. I am going to let it dry (inside) for few days, at least until I have the weather to put my geophone underground. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Dissipation of Seismic Waves From: "Bob Hancock" carpediem1@......... Date: Wed, 25 Oct 2006 10:19:58 -0700 Hi John - Very Interesting.......I plotted out the data using the two formulas 1/r^2 and 1/sqrt r for distances up to 15000 km. This helps explain the prominence of the Love and Rayleigh waves on teleseismic events, and why I am loosing the P and S waves in the background on some events. You have given me a lot to study so it take a while to absorb all of it, but then again, that's the challenge of life.....learning new things. Thanks Again - your help is SINCERELY APPRECIATED !!! Bob -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of John or Jan Lahr Sent: Tuesday, October 24, 2006 23:50 To: psn-l@.............. Subject: Re: Dissipation of Seismic Waves __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Katla volcano webcam From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Wed, 25 Oct 2006 17:25:49 +0000 Hi all I just found out that they are now monitoring Katla volcano with a webcam. You can see the current view here, http://www.ruv.is/katla/ The page is in Icelandic and requires java to work. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: My seismometer vault solution From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Wed, 25 Oct 2006 17:44:39 +0000 Hi I am dealing with a lot of sand. Problay around 3 - 5 kg. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: My seismometer vault solution From: "Erich Kern" efkern@............. Date: Wed, 25 Oct 2006 11:10:33 -0700 All the more reason to get rid of as much moisture as possible. 5 kg is not what I would call a lot of sand. It can easily be dried in the kitchen oven. Once the sand is sealed in a bucket all the dessicant packs you can fit in it will not get rid of the moisture. Better do it before it's sealed. Erich ----- Original Message ----- From: "Jón Frímann" To: Sent: Wednesday, October 25, 2006 10:44 AM Subject: Re: My seismometer vault solution Hi I am dealing with a lot of sand. Problay around 3 - 5 kg. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: My seismometer vault solution From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Wed, 25 Oct 2006 18:50:33 +0000 Hi I will figure out how to dry the sand. The soil type where I am placing my geophone is intresting, appears to be mostly sand and rocks. At least my shuffle didn't go deep into the ground when I was testing it this moment. I am going to start diggin the hole tomorrow if the weather allows. Regards. -- Jón Frímann http://www.jonfr.com http://www.simnet.is/jonfr500/earthquake/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Earthtides From: Bill S wls@......... Date: Wed, 25 Oct 2006 15:17:30 -0400 Stephen, Thanks, it was just what I was looking for. Bill S At 01:54 PM 10/24/2006, you wrote: >I think this is what your looking for: > >http://aiuas3.unibe.ch/dpgm/zm_graph_tide.html > > Stephen > PSN Station #55 > >Bill S wrote: >>Hi, >>Does anyone know of a site showing live earthtide measurements? >>Bill S >> >> >>__________________________________________________________ >> >>Public Seismic Network Mailing List (PSN-L) >> >>To leave this list email >>PSN-L-REQUEST@.............. with >>the body of the message (first line only): unsubscribe >>See >>http://www.seismicnet.com/maillist.html >>for more information. >> Stephen,
Thanks, it was just what I was looking for.
Bill S


At 01:54 PM 10/24/2006, you wrote:

I think this is what your looking for:

http://aiuas3.unibe.ch/dpgm/zm_graph_tide.html

  Stephen
  PSN Station #55

Bill S wrote:
Hi,
Does anyone know of a site showing live earthtide measurements?
Bill S


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Public Seismic Network Mailing List (PSN-L)

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Subject: Re: weather From: Richard Webb dwebb002@............. Date: Wed, 25 Oct 2006 16:20:38 -0400 Ted, Could be something as simple as wind in the trees disturbing the ground. I see the same problem because my vault, although 6 feet below ground level is in a wooded area and roots go quite deep. Dick tchannel wrote: > Hi All, I was so happy with my sensor, over the last few day. I had > a major problem with thermos, which disappeared with my insulated > box. This question has to do with weather changes, and why that > effects noise. > A day ago the tract was quiet at night and a little bit of noise > during the day time and city activities. > Many hours ago a cold front came thru, arriving at 8:00 pm with > winds. The trace went from quite to noisy several hour ahead of the > front. You could look at the trace and see the change as the front > got closer. This weather should move out in the next 24 hours. So I > expect things will go back to normal. > > I don't understand, what is stimulating the sensor. > 1. Does it respond to barometric pressure changes? > 2. When wind is part of the storm, and the wind moves the trees, is > this transferred thru the ground to the sensors as earth movements? > 3. Would a bolt of lightening be displayed on the trace? > > As a front approaches it is like the atmosphere starts to fill with > electromagnet noise. I'm just trying to understand what creates it. > Inside the garage and inside the box it seem so isolated, no wind, no > air current, no vibrations or physical movements. Yet the sensor can > see a front hours before it arrives. > Thanks, Ted __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: weather From: ChrisAtUpw@....... Date: Wed, 25 Oct 2006 20:11:10 EDT In a message dated 2006/10/25, tchannel@.............. writes: > Subj:weather > Hi All, I was so happy with my sensor, over the last few day. I had a > major problem with thermos, which disappeared with my insulated box. This > question has to do with weather changes, and why that effects noise. > A day ago the trace was quiet at night and a little bit of noise during the > day time and city activities. > Many hours ago a cold front came thru, arriving at 8:00 pm with winds. The > trace went from quiet to noisy several hour ahead of the front. You could look > at the trace and see the change as the front got closer. > I don't understand, what is stimulating the sensor. > 1. Does it respond to barometric pressure changes? Hi Ted, Horizontal seismometers have a relatively low sensitivity to baromatric pressure changes. Vertical sensors are effected directly and may show x100 the noise. > 2. When wind is part of the storm, and the wind moves the trees, is this > transferred thru the ground to the sensors as earth movements? A front / storm has quite violent local turbulence. The quite small absolute pressure changes effect large ground areas. The wind noise is right across the spectrum and it effects everything from the phone wires to whole mountains. Tall isolated trees pick up wind noise very well. So do tall buildings. The frequency of the noise is proportional to the wind velocity, but inversely proportional to the effective width of the tree, building etc. > 3. Would a bolt of lightening be displayed on the trace? This is likely to be a sharp transient - you may also see a second sound signal. > As a front approaches it is like the atmosphere starts to fill with > electromagnet noise. I'm just trying to understand what creates it. > Inside the garage and inside the box it seem so isolated, no wind, no air > current, no vibrations or physical movements. Yet the sensor can see a front > hours before it arrives. A sheet of writing paper may be 0.1 mm thick. You seismometer can sense movements which are less than 1/1000 of this over many seconds. If your garage was not dead quiet, your seismometer would be way off scale. A storm front has huge eddies of air weighing hundreds to thousands of tons churning about. Air is quite heavy stuff. Regards, Chris Chapman In a me= ssage dated 2006/10/25, tchannel@.............. writes:

Subj:weather
Hi All,   I was so happy with my sensor, over the last few day. I=20= had a major problem with thermos, which disappeared with my insulated box. T= his question has to do with weather changes, and why that effects noise. A day ago the trace was quiet at night and a little bit of noise during the= day time and city activities.
Many hours ago a cold front came thru, arriving at 8:00 pm with winds. The=20= trace went from quiet to noisy several hour ahead of the front. You could lo= ok at the trace and see the change as the front got closer. 
I don't understand, what is stimulating the sensor.
1.  Does it respond to barometric pressure changes?


Hi Ted,

       Horizontal seismometers have a relative= ly low sensitivity to baromatric pressure changes. Vertical sensors are effe= cted directly and may show x100 the noise.

2.  When wind is part of=20= the storm, and the wind moves the trees, is this transferred thru the ground= to the sensors as earth movements?