## PSN-L Email List Message

Subject: Re: Springs again
From: Bobhelenmcclure@.......
Date: Wed, 18 Jul 2007 21:33:56 EDT

```Hi Paul,

Have you looked at my web pages at

_http://www.jclahr.com/science/psn/mcclure/index.html_
(http://www.jclahr.com/science/psn/mcclure/index.html)

There you will find a description and picture of my vertical sensor,  which
operates at a period of about 5 seconds. By the way, the coil is the most  of
the mass.

Also there is a page describing my spring calculator for use in  vertical
calculator. The trick to getting a long period is to arrange the geometry of the  spring
so that a decentering force is created to offset most of the restoring  force
of the spring. A zero-length spring automatically does this. You have to
relocate the support point of the spring if it is not zero length. For an AS-1
type of seismometer, the upper end support of the spring should not be directly
above the hinge, but back of it. This adjustment is very delicate if long
period  is the goal.

For a sensor of the type you describe, the following links may be  helpful:

_http://quake.eas.gatech.edu/Instruments/LPVERT0.htm_
(http://quake.eas.gatech.edu/Instruments/LPVERT0.htm)

_http://www.eas.slu.edu/People/STMorrissey/index.html_
(http://www.eas.slu.edu/People/STMorrissey/index.html)

Cheers,

Bob

************************************** Get a sneak peek of the all-new AOL at
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Hi Paul,

Have you looked at my web pages at

http://www.jcl=
ahr.com/science/psn/mcclure/index.html

There you will find a description and picture of my vertical sen=
sor,=20
which operates at a period of about 5 seconds. By the way, the coil is the m=
ost=20
of the mass.

Also there is a page describing my spring calculator for use in=20
vertical seismometers. You would do well to download and experiment with the=
=20
calculator. The trick to getting a long period is to arrange the geometry of=
the=20
spring so that a decentering force is created to offset most of the restorin=
g=20
force of the spring. A zero-length spring automatically does this. You have=20=
to=20
relocate the support point of the spring if it is not zero length. For an AS=
-1=20
type of seismometer, the upper end support of the spring should not be direc=
tly=20
above the hinge, but back of it. This adjustment is very delicate if long pe=
riod=20
is the goal.

For a sensor of the type you describe, the following links may b=
e=20

http://quake.ea=
s.gatech.edu/Instruments/LPVERT0.htm

http://www.eas=
..slu.edu/People/STMorrissey/index.html

Cheers,

BobGet a snea=
k peek of the all-new AOL.com.
```