In a message dated 23/12/00, mja6042@............. writes: > When viewing the output with SDR I am getting about 80 to 100 counts of > continuous noise. I don't know what the frequency of the noise is but the > period is too short to see on SDR. > Is this noise level abnormally high and does anyone have any suggestions on > how to reduce the noise. Hi there Mark, This noise level is much greater than I would normally expect. Check your power supplies for noise with AC DVM. You aren't using the computer power supplies are you? They can be very noisy. Also check the earth connection. Do you have access to an oscilloscope? A quick look at the waveform, frequency, etc. can be very helpful. Check that you have the correct values of gain resistors in the feedback circuits. I have been sold resistors which are a factor of 10 out. Double check that you have made the circuits properly. Short the input to the ADC and check the noise level. Then check with the input to the first amplifier shorted, but everything else connected. If this doesn't cure it, you will need to short the input to the last OpAmp, check the level and work back chip by chip until you find the problem circuit. Look for mains / computer noise, oscillations, a dud OpAmp, dry solder joints, noisy resistors, faulty capacitors, etc. Hope that these suggeations are of some help, Chris __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>