Mark, Jim and Others...

With the input shorted at the A/D board there should only be +- 4 or 5
counts of noise. Either Mark has a ground loop problem or his Amp is
oscillating.

-Larry Cochrane
Redwood City, PSN

----- Original Message -----
From: "Jim Hannon" 
To: 
Sent: Saturday, December 23, 2000 6:05 AM
Subject: Re: Amplifier noise?


> Mark,
> I think that what you are seeing is about the noise level of Larry,s  16
> bit A/D card. You can check this by operating the A/D card with it's input
> shorted. Check the noise level and see how it compares to the noise when
> your amplifier is connected.
>
> At 08:53 PM 12/22/00 -0600, you wrote:
>
>
> >Hello Everyone,
> >
> >
> >Recently I finished construction on my first seismometer.  I used
> >schematics off of Larry Cochrane's web site to wire wrap the amplifier:
> >http://psn.quake.net/sgsumamp.gif and http://psn.quake.net/sgproc.gif
> >
> >I housed the amplifier in a steel box, grounded to analog ground on the
> >amplifier board.
> >
> >I have the output of the amplifier connected to Larry's 16 bit A to D
board
> >with about 16 feet of shielded wire.  The shield, around the wire, is
> >grounded to the case of my computer.  When viewing the output with SDR I
am
> >getting about 80 to 100 counts of continuous noise.  I don't know what
the
> >frequency of the noise is but the period is too short to see on SDR.
> >
> >Is this noise level abnormally high and does anyone have any suggestions
on
> >how to reduce the noise.
> >
> >Thanks for your time!
> >
> >Mark
> >
> >
>
> Jim Hannon
> http://soli.inav.net/~jmhannon/
> 42,11.90N,91,39.26W
> WB0TXL
>
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