Hello Folks,

I just completed a crude N=8 Gain x1 LPF with a knee at 10Hz (about)
and my first try went well. I think this is BUTTERWORTH.

http://gmvoeth.home.mchsi.com/LATEST/CIRCUIT/GVA_CIRCUIT.HTML

I used the ARRL formulas as well as the following test equipment.


DMM == Radioshack 22-812 (seems very good)
for everything but capacitors.

Capacitor Meter==WEB-TRONICS.COM MY6013A
Don’t know if this meter still exists.
Only For Capacitors

Electrolytics Are not recommended for signal filters only power filters.

USE Metal Film ( I did )

As a first try at this N=8 I now feel safe in using a 100SPS rate
instead of the 500sps I was previously using.

This kind of filter is strongly recommended (by ME)
between the A/D converter and Amplifier
if you live in urban/suburban noise areas.

You need to use trimmer caps (like 10K 15 to 20 turns)
with added fixed resisters to achieve as close as possible
to the desired resistance values within the filter circuit.
Otherwise, it will be much more difficult to adjust things.
I do not know how otherwise to get an exact value resistor.

Cheers & Happy Holidays & New Year  etc... usw...
geoff

__________________________________________________________

Public Seismic Network Mailing List (PSNLIST)

To leave this list email PSNLIST-REQUEST@.............. with 
the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html for more information.