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What's wrong with the vibration shaker?

  1. Jan 10, 2015 #1
    Hi There,
    I have a VTS(vibration test system)-100 shaker. To make sure it works correctly, I have done a acceleration frequency response test for the bare shaker. In which, I place an accelerometer on the top of the shaker platform, use a function generator and amplifier to drive the shaker at sweeping frequency from 2 Hz to 6000 Hz. I also use a polytech laser vibrometer to detect the displacement of the point on the shaker platform close to the location of the accelerometer. I use LABVIEW to control the oscilloscope and function generator. Attached are my result. From the acceleration frequency response graph, I see several peaks indicating the "resonance" frequency, according to the vibration theory, the acceleration should be a continuous function of the frequency, it should be a smooth line without any resonance peaks. What is wrong with my measurement? or the shaker is bad? I have made sure the accelerometer is good.
    Thanks.
    Mike
     

    Attached Files:

  2. jcsd
  3. Jan 10, 2015 #2
    could you be getting harmonics? do these same results show on every try?
     
  4. Jan 11, 2015 #3
    I suspect that the difficulty arises from trying to make an overly simple mathematical model fully describe a real physical system. All real systems have infinitely many modes of vibration, yet we never develop models of that level of complexity. You have just run headlong up against reality!
     
  5. Jan 11, 2015 #4

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    Looking at a picture of the little beast, you could be getting mode plus harmonic for the bracket.
     
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