I use PSD function to get the amplitude spectrum of accelerometers on a pump, thru a DAQ device.
im sampling at 25600hz, using 512 samples once every second for the spectrum.
i dont do any averaging, as i had some difficulties making it work as i expected.
even when the pump is at standstill im picking up high amplitudes in the lowest or second lowest frequency bin.
see attached pic: frequency spectrum mms2
when i do frequency domain integration, these amplitudes become more prominent. note that i set the 0hz bin to zero after the integration, as i didnt figure out how to do integration at 0hz.
see attached pic: frequency spectrum mms
see attached pic: frequency spectrum mms zoomed
If i turn off windowing; hanning -> rectangular, then these amplitudes almost disappear. maybe because spectral leakage smooths it out? blackman window made them larger than hanning.
Is there some known reason this could happen, is there some simple way to correct? my plan forward is to increase frequency resolution (use 8000 samples maybe) enough that i can drop the lowest bins from measurements, hopefully the pc will handle it.
i dont have VI available to post as im writing topic.