From: Brett Nordgren brett3nt@.............
Subject: Re: tin cries


Randall,
hat amount of dither do you think would be adequate?  I suppose it=20
ould best be expressed as variation in the spring strain, or in=20
hatever other way you suggest.
hanks,
rett
At 06:47 PM 8/15/2011, you wrote

   I see this process as a potential energy function that is very=20
 much like the vertical seismometer, except turned upside=20
 down.  Extending the spring and then releasing, it does not return=20
 to a perfectly defined equilibrium point; i.e., it finds a new very=20
 slightly different places to come to rest because of the 'ratchety'=20
 nature of the restoring force at the very low levels.  Much of my=20
 experimental work is consistent with this 'heretical' viewpoint,=20
 and I think it is the very reason, Brett, you would do well to try=20
 and do some low level dithering of your instrument.
Hi Brett,=20
    I would suggest a purely practical approach. Add another small winding =
to force feed=20
back coil. Drive it from a variable AC sinewave current source at 5x to 10x=
 the cutoff=20
frequency of your Low Pass fllter, so that you can't see any oscillatory re=
sponse. Then=20
monitor how the very long period background noise detected changes, as the =
drive=20
current is increased ?
    Regards,
    Chris=20





=
From: Brett Nordgren brett3nt@bno=
rdgren.org

Subject: Re: tin cries





Randal=
l,
What amount of dither do you think would be adequate?  I suppose it=20
could best be expressed as variation in the spring strain, or in=20
whatever other way you suggest.
Thanks,
Brett

At 06:47 PM 8/15/2011, you wrote

<clip>
>   I see this process as a potential energy function that is very=20
> much like the vertical seismometer, except turned upside=20
> down.  Extending the spring and then releasing, it does not return=20
> to a perfectly defined equilibrium point; i.e., it finds a new very=20
> slightly different places to come to rest because of the 'ratchety'=20
> nature of the restoring force at the very low levels.  Much of my=20
> experimental work is consistent with this 'heretical' viewpoint,=20
> and I think it is the very reason, Brett, you would do well to try=20
> and do some low level dithering of your instrument.
Hi Brett, 
    =
I would suggest a purely practical approach. Add another small winding to f=
orce feed 
back coil. Drive it from a variable AC sinewave current sou=
rce at 5x to 10x the cutoff 
frequency of your Low Pass=
 fllter, so that you can't see any oscillatory response. Then <=
/PRE>
monitor=
 how the very long period back=
ground noise detected <=
/TT>changes, as the drive 
=
    Regards,
    Chris =