I am running an fft on 60 seconds of data sampled at 1289Hz. The fft is run every second on a single channels fifo buffer which is also updated every second. The algorithm used is numpy rfft with a numpy blackman window. The fft output is normalized to the max fft value. This is all on a raspberry pi 4 with custom adc board that uses an AD4114. Am sampling 8 channels (16 in differential mode) as fast as the AD4114 can go which works out to 10.312kHz.
The following screen shots are with a 20Hz sign wave applied to one of the channels. Similar low magnitude peaks appear with
real data a transducer attached to the input. There are low magnitude peaks centered exactly 1Hz apart right on top of each whole number. Is this normal? Like a normal artifact of the fft? Possibly something wrong with my data? I am a casual fft user and am hoping someone may have some advice for me. Thank you very much : )