In a message dated 12/09/00 15:43:20 GMT Daylight Time, jmhannon@........ 
writes:

> The second two 0.1 UF capacitors associated with the second 
> filter op amp should be changed to 0.0991 UF. You will
> need to measure and test select the capacitors and possibly parallel parts
> to get within at least 5% of the values specified.

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
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