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  1. Balplus

    Signal Processing Problem

    Thanks for all your help and patients. I do consider sidebands important. The sideband separation frequency identifies the problem component in the machine. Like I said in my original post, I was told in a class once that sidebands are false frequencies in machine vibration signals (a false...
  2. Balplus

    Signal Processing Problem

    Vibration signals often looks "clipped" and/or distorted because, as far as I know, there is no such thing an a linear machine. Because of the different stiffnesses about the circumference of a machine, along with different types of preloading on the machine, such as misalignment and distorted...
  3. Balplus

    Signal Processing Problem

    Skogsgurra, I was addressing you in my last post -- sorry for the mixup. I understand that rotorbar pass is a real frequency as well as the 120 Hz torque pulse frequecy. I would expect a peak in the spectrum at 120 Hz and a peak at rotorbar pass frequency. My question is ---- Are the 120 Hz...
  4. Balplus

    Signal Processing Problem

    Logbook, thanks for the reply. Yes, the data we collect for vibration analysis is very low frequency compared to the electronic frequencies you electornic wizards work with. I usually take 2048 samples (800 line FFT). The frequency span is 0 to 2 KHz. The sidebands show up even at 8192...
  5. Balplus

    Signal Processing Problem

    Thanks for the help so far. I am still not clear on the subject. My background is in vibration analysis and this questions relates to mechanical vibrations that produce an electrical signal from an accelerometer. Keep in mind that this signal represents the mechanical motion of a machine and...
  6. Balplus

    Signal Processing Problem

    I was told in a class once that sidebands in an FFT (frequency spectrum) are not true frequencies, but are created in the FFT process because of the way the FFT algorithm handles modulation. Is this true?

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