Joh

I am trying to measure the noise in an analog circuit using the AD2 with BNC Adapters (CH 1, 10x Attenuation, DC Mode, Ground-Spring). I enabled the FFT-View and activated "Linear RMS Averaging" over 10 Samples and measured in "Repeated Mode" without trigger. The measured circuit can produce a voltage between 0-3.2V but should output approximately a stable 1.55V during test conditions. I expected to see one or more frequencies in the FFT that produce most of the noise. However I was taking three measurements with three different sampling rates and got three very different looking FFTs. 1. Measuring with Samplingrate 20kHz: FFT shows a peak at ~8kHz 2. Measuring with Samplingrate 50kHz: FFT shows a peak at ~18kHz 3. Measuring with Samplingrate 100kHz: FFT shows a peak at ~32kHz In my opinion the location of the peaks in the FFT should not depend on the samplingrate. Now I am unsure whether the FFT peaks are simply measurement artifacts of if I am missing something. I attached screenshots of the three measurements. Thank you for any help in advance!