PSN-L Email List Message

From: Karl Cunningham karlc@.......
Date: Mon, 11 Sep 2000 14:59:26 -0700

Hi Jim --

I agree with Sean-Thomas regarding the use of Bessel filters.  Other kinds
of filters will distort the waveforms.

I don't think the filter shown in the schematic you referenced is even a
Butterworth.  I entered the component values into a simulation program and
found it has an 8:1 peak near its cutoff frequency.  That's not good for
seismic work.


At 01:52 AM 9/11/2000 EDT, you wrote:
>There is a preamp and 4th order 1.0 Hz, low pass filter schematic by A.S. 
>Loomis at  Has anyone had 
>experience with this circuit?  Is it possible to change it from a 1.0 Hz low 
>pass filter to a 10 Hz low pass filter?  If so, what component values should 
>be changed to accomplish this?  I assume it is a good design.
>Any assistance would be very much appreciated.
>Jim Allen


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Larry Cochrane <cochrane@..............>