Hi

I've got a question concerning an ECG measurement I did at a laboratory lesson recently. The amplifier was a 3-OP circuit with two adjustable potentiometers. We were to adjust those to get a minimal common mode signal at two different frequencies (100 Hz and 1kHz). What I can't understand is why you have to do this att two frequencies?

 

If you are in a country that uses 50 Hz power, the the 100 Hz test was to eliminate power supply interference. It should be valid for 120 Hz as well. The 1K test was to insure any interfering frequencies outside the range of interest was eliminated.