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. Regards, Karl 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 http://www.info2000.net/~aloomis/seisfilt.htm. 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 __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>