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