Hi Chris and all,

Thanks for all the helpful references!  I was looking for a test that would
roughly indicate
pivot sensitivity; but where, there is no pickup coil (electronics),
dampening etc....i.e.,
a "base" test of the instruments pivot/boom/mass in its unfinished state,
just to
evaluate whether the setup is worth further pursuing.

After going through John Lahr's web site...I "gather" that if; say a bond
paper item of
about ~2" x 1/2" is laid atop the mass, and one can VISUALLY see a immediate

deflection of the mass; then the sensitivity must be quite good.  Does this
sound
logical; or maybe I'am missing something?

The test vertical instrument here is using acouple hard drive disk/s inner
hole circle surfaces
with the axis being a 1/4" rod...i.e, a rolling pivot; laid out somewhat
like the Georgia
Tech vertical "demonstrator" seismometer...but not using flexure strips as
the pivot.
I could see roughly a initial 1/16" deflection.

Meredith Lamb


On 10/31/07, ChrisAtUpw@.......  wrote:
>
>  In a message dated 31/10/2007, paleoartifact@......... writes:
>
> 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?
>
>  Hi Meredith,
>
>     Weight lift calibration is used on AS-1 seismometers. See links from
> http://jclahr.com/science/psn/as1/
>     Far from being crude, it should be accurate at least to a few%. I
> favour using weights made from known lengths and diameters of copper wire,
> bent to give three point contacts. You can use fine nylon fishing line to
> lift the weight. Sewing thread tends to twist.
>     You can also calibrate horizontal seismometers using a wire weight
> suspended on a 90 deg V silk / cotton thread. Having set the system up, you
> release the mass by burning the thread.
>
>     Regards,
>
>     Chris
>
Hi Chris and all,
 
Thanks for all the helpful references!  I was looking for a test that would roughly indicate
pivot sensitivity; but where, there is no pickup coil (electronics), dampening etc....i.e.,
a "base" test of the instruments pivot/boom/mass in its unfinished state, just to 
evaluate whether the setup is worth further pursuing.
 
After going through John Lahr's web site...I "gather" that if; say a bond paper item of
about ~2" x 1/2" is laid atop the mass, and one can VISUALLY see a immediate 
deflection of the mass; then the sensitivity must be quite good.  Does this sound
logical; or maybe I'am missing something?
 
The test vertical instrument here is using acouple hard drive disk/s inner hole circle surfaces
with the axis being a 1/4" rod...i.e, a rolling pivot; laid out somewhat like the Georgia
Tech vertical "demonstrator" seismometer...but not using flexure strips as the pivot.
I could see roughly a initial 1/16" deflection.  
 
Meredith Lamb

 
On 10/31/07, ChrisAtUpw@....... <ChrisAtUpw@.......> wrote:



In a message dated 31/10/2007, paleoartifact@......... writes:

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?

Hi Meredith,
 
    Weight lift calibration is used on AS-1 seismometers. See links from  http://jclahr.com/science/psn/as1/

    Far from being crude, it should be accurate at least to a few%. I favour using weights made from known lengths and diameters of copper wire, bent to give three point contacts. You can use fine nylon fishing line to lift the weight. Sewing thread tends to twist.

    You can also calibrate horizontal seismometers using a wire weight suspended on a 90 deg V silk / cotton thread. Having set the system up, you release the mass by burning the thread.  
 
    Regards,
 
    Chris