PSN-L Email List Message

Subject: RE: spike problem
From: "Timothy Carpenter" geodynamics@.......
Date: Mon, 5 Jun 2006 01:52:42 -0400


You should NOT be connecting the shield to the water pipe -- it should =
connected to ground on the amplifier board. Consult the specifications /
user manual for the amplifier board to see where you should make the
connection -- I'd suspect that the connection should be made to the =
"power ground".

Do you have the geophones connected single-ended or double-ended (full
differential). If your board has the capability, I'd recommend that your
connections be full differential.

When I mentioned that some of your signals had the appearance of a
capacitive discharge, I didn't mean to imply that you had capacitors in =
geophones. If there is anything in the geophone housing that looks like =
capacitor, my bet is that it's a damping resistor. Such resistors are
installed to reduce the resonance of the geophone when signals come in =
at or
near its natural frequency. You can see the effects of different =
on the geophone response at:

On the chart, response A is for the case with no resistor installed. =
Cases B
through D are for successively higher resistances. If I was using this =
of geophone for monitoring earthquake activity, I'd remove the resistors =
just to gain that bit of additional sensitivity throughout the =


Timothy Carpenter
5043 Whitlow Court
Commerce Township, Michigan 48382

-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... =
Behalf Of J=F3n Fr=EDmann
Sent: Sunday, June 04, 2006 12:46 PM
To: psn-l@..............
Subject: Re: spike problem


I have connected the shield in the cable to the ground. Trugh a heating
oven (or how it is spelled / word over it) in the room, it uses hot
water so it is ideal for this type of connection to the ground. That is
going to elimiate the shield problem chargeing up, at least it I hope it
does. The connection to the ground is farly good. There is paint on the
heating oven, but I don't think that is a problem.

Now I only have to fix the larger spikes. Or replace the capacitor that
is possible leaking, this spikes happens on all the channels, so I am
problay going to have to replace them all. If that can be done.

J=F3n Fr=EDmann


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