I am doing some frequency analysis of a vibration signal from a spinning rotor,
I am expecting to see peaks corresponding to the rotational frequency of the rotor. So the fundamental frequency should be ~0.7Hz, then I am assuming I should then see multiples of this corresponding to the harmonics?
I can clearly see peaks at ~ 1.4Hz, 2.8Hz, 3.5Hz, and 4.2Hz but nothing at 2.1Hz which I cant understand
I am not sure whether the explanation for this can be explained physically or if its related to my sensor setup / analysis methods? I dont think it is related to the frequency resolution since this is around 0.03 Hz which seems suitably low.
It seems likely to me that there is some kind of weighting to specific harmonics and the 2.1Hz harmonics is somehow damped but I can't think why this would be the case.