Non-decaying Harmonics in Vibration Signal I am analyzing vibration data collected by an accelerometer positioned in a stamp press machine. The fundamental frequency is around 10 Hz. The problem here is that when I take the FFT of the data I see harmonics of the fundamental frequency until 5000 Hz every 10 Hz (of course). I would expect some visible harmonics in low-frequency but with a decaying behavior until, at some point, it disappears. I attached 2 figures. The first one with a zoom from 0 to 1000 Hz and the other from 4000-5000 hz. Note that the Harmonics dominate the signal.

   



And here is a sample of the data:



I have being trying to convince myself that is normal but I can´t. What do you guys think? Can it be an effect of something that I should discard? 

Thank you!
Well, looking at your time-domain signal, it looks a bit similar to a pulse train. And the Fourier Transform of a Pulse train with distance T is a Pulse train with distance 1/T

Hence, if you see a pulse every 10Hz, this corresponds to pulses every 0.1seconds in the time domain. That's what the time-domain signal looks like.