Chris, I was worried that the 4 1 Meg would be miss interpeted. I am referring to the four 1 Meg Ohm resistors not to a 4.1 Meg ohm resistor. My eyes are not working too well, upon closer examination of the schematic the resistor values look like 1M6 rather than the 1MG I thought I was reading. This is a notation I have not seen too often for 1.6 Meg. That value makes more sense because it gives the filter a 1 Hz 3 dB response than the 1.59 Hz I had calculated using 1 Meg Ohms. Anyway when I get to work tomorrow I will go over my calculations and also try to figure out why Karl and I are getting different results from our analysis. As for the capacitor values 0.0991 UF is what the equations give. I did not try and round off or pick nearest values. All of this illistrates the difficulty of building active filters and getting the desired response. You have to account for all the component tolerances and check to see how badly it messes up the desired response. Some circuit topologies are more tolerant to component variations than others. So even the type of circuit needs to be considered. >Jim, > > ??? Sorry, but I don't quite understand. 0.0991 UF is within 1% of 0.1 >UF. > > > The 1 Hz design is easily changed to any other frequency within > > reason by dividing the value of the 4 1 Meg Ohm resistors by the > > desired frequency. For example if you want a 5 Hz low pass filter > > you would use 200K resistors instead of 1 Meg. > > Where is the 4.1 M Ohm coming from? The diagram of the four pole filter >gives pairs of 1.6 M Ohm input resistors. Can you confirm the R value for 1 >Hz please? > > Regards, > > Chris Chapman >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. Jim Hannon http://soli.inav.net/~jmhannon/ 42,11.90N,91,39.26W WB0TXL __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>