PSN-L Email List Message

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







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@....... =
To: psn-l@..............
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

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