Larry and J=F3n,

I think Larry may have focused on the root of the problem -- that is,
gounding. In looking at your seismic traces, J=F3n, I see occasional =
signals
where there is an initial spike that is accompanied by a slow decay over =
a
period of a minute or more. This looks suspiciously like a leaking
capacitor. In a recent case, geophones were emplaced by others using
shielded cables on the order of 500-feet in length, the output was =
terrible.
After much troubleshooting and questioning of the folks who installed =
the
system, I found out that they had never brought the shield to ground. =
One of
the characteristics of their output was the same spike and subsequent =
decay
over time. It appears that the ungrounded shield was building up a =
charge
(especially during thunderstorms) that would slowly bleed off over time.

Regards,

-Tim-

Timothy Carpenter
GeoDynamics Consultants, Inc.
Commerce Township, Michigan 48382

-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... =
On
Behalf Of Larry Cochrane
Sent: Saturday, June 03, 2006 8:57 PM
To: psn-l@..............
Subject: Re: spike problem

Hi J=F3n,

Did you connect up the shield (screen) of the cable to the ground of the
Amp/Filter=20
board?

Regards,
Larry Cochrane
Redwood City, PSN

J=F3n Fr=EDmann wrote:
> Hi all
>=20
> The spike problem still exist. :(
> I am out of ideas what this might be. Also, after I did change to
> screened cable I have been seeing alot of smaller spikes with regular
> intervals, those smaller spikes happen with 10 to 20 seconds spaces
> between them. That might becose of the computer (serial port issue), =
but
> I am not sure.
>=20
> Regards.

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