PSN-L Email List Message

Subject: Re: Mass deflection weight test
From: "Geoff" gmvoeth@...........
Date: Thu, 1 Nov 2007 16:29:55 -0700

Yes, there is this very large OLD geospace ( Texas I think )
Seismometer that weighs about 500 lbs avodupoise
and you test it by taking a known weight
( 1gm ( metric ) ball bearing ) on a string ( dental floss ).
 using the string you place the
weight upon an adjusting screw mounted to the
suspended mass then let it rest till all motion
ceases then you yank on the string to instantly
remove the small weight. This will simulate an
impules of a one way acceleration relating directly
to the mass removed. You can then look at the trace
and see if free period and damping and sensitivity
are ok or adjustments or repairs are necessary.
This barontosaurous of geophones is actually quite good
but need a special home underground or dampness
( exposure ) will destroy it.
It is also extremely difficult to move around being 500lbs.
sort of like one of those mystical magical squeegee
sharpening machines you boss sometimes wants you to find.
If it happens to weigh 500 lbs and is bolted down
it might take all day to deal with.

I have the best way to simulate this with smaller
geophones is to pulse it with a battery limiting
the current flow ( resistor ) to whatever produces 100
or so microvolts across the geophone.
You just need to be consistant with the
chosen form of testing.

If you really want to get it ringing
with minimal damping
zap ( momentarily not continuous )
it with a 9V battery.
( magnet spring type only )

----- Original Message ----- 
From: "meredith lamb" 
Sent: Wednesday, October 31, 2007 2:57 PM
Subject: Mass deflection weight test

> Hi all,
> Quite some time back, their was a reference (text) regarding a rough
> "deflection" test;
> where a small item (feather or something similar), was placed upon the mass
> of a
> vertical seismometer, and that displacement was a rough measure of (I think)
> of its
> crude sensitivity?
> Anybody have a knowledge of such; or a exact PSN email reference...or their
> experiences?
> Thanks, Meredith Lamb

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