## PSN-L Email List Message

Subject: Re: Spring Damping
From: Bobhelenmcclure@.......
Date: Tue, 24 Jul 2007 00:27:39 EDT

```The discussion of the effects of spring vibration made me look up the
following paragraph from the Physics section of the downloaded manual. It seems
that vibration has no first order effect on vertical sensor performance if the
spring is zero length.

Bob

LaCoste & Romberg
INSTRUCTION MANUAL
MODEL G & D GRAVITY  METERS
_Http://www.LaCosteRomberg.com_ (http://www.LaCosteRomberg.com)

"An important feature of the zero length spring suspension is  its
insensitivity to longitudinal and transverse vibrations  (Harrison
1960, LaCoste 1967). Consider the spring to be made of  identical
masses with segments of weightless zero length spring between  the
masses. The top end of the spring is attached to A and the bottom
to  B. Since the spring segments are zero length springs, the forces
each spring  exerts on the adjacent masses are proportional to the
spring length.  Therefore, if the masses are equally spaced vertically,
the vertical  component of force exerted on each mass will be
zero regardless of its  horizontal position or horizontal motion.
Also, the vertical components of  force are proportional to the
vertical component of spring length. (The  vertical component of
the force vector remains the same.) Also, the vertical  force on A
and B will be independent of any horizontal  motions."

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The discussion of the effects of spring vibration made me look up the=20
following paragraph from the Physics section of the downloaded manual. It se=
ems=20
that vibration has no first order effect on vertical sensor performance if t=
he=20
spring is zero length.

Bob

LaCoste & RombergINSTRUCTION MANUALMODEL G & D GRAVITY=20
METERSHttp://www.LaCosteRomberg.com
"An important feature of the zero length spring suspension is=20
itsinsensitivity to longitudinal and transverse vibrations=20
(Harrison1960, LaCoste 1967). Consider the spring to be made of=20
identicalmasses with segments of weightless zero length spring between=20
themasses. The top end of the spring is attached to A and the bottom=
to=20
B. Since the spring segments are zero length springs, the forceseach spr=
ing=20
exerts on the adjacent masses are proportional to thespring length.=20
Therefore, if the masses are equally spaced vertically,the vertical=20
component of force exerted on each mass will bezero regardless of its=20
horizontal position or horizontal motion.Also, the vertical components o=
f=20
force are proportional to thevertical component of spring length. (The=20
vertical component ofthe force vector remains the same.) Also, the verti=
cal=20
force on Aand B will be independent of any horizontal=20
motions."Get a sneak peek=
of the all-new AOL.com.
```