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In a vibration measurement of a rotating blade, I have the following information. The vibration signal is measured using an ICP accelerometer which has the following specification

  • Measurement range: 50g
  • Sensitivity: 100 mV/g
  • max output voltage: ±5V
  • Broadband resolution: 100e-6g

The variance of the acquired signal is

$$var_{aq} = var_{acl} + var_{adc} + var_{sig} \approx 6.2e-4 g$$

  • $var_{acl}$ = variance of noise in the accelerometer
  • $var_{adc}$ = variance of the ADC noise (quantization, jitter)
  • $var_{sig}$ = variance of the vibration acceleration of the blade.

Assuming that $var_{acl} \approx \sqrt{\text{broadband noise of accelerometer}} = 1e-8 \text{g_rms}$.

From the specification sheet of the ADC, for the used input gain of 30db and sampling frequency = 51.2Hz, the $var_{adc} = 1e-12 \text{V_rms}$

Can anyone please help, how can I calculate the variance of vibration acceleration of the blade $var_{sig}$?

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  • $\begingroup$ Hi, welcome to Engineering. If I understand correctly your question can be reduced to "How can I convert $var_{adc}$ units ($V_{rms}$) to $g_{rms}$ which are compatible with the rest of the quantities. " $\endgroup$ – NMech Dec 11 '20 at 6:47
  • $\begingroup$ Yes that would be one thing to conver the Vrms to grms. Do i need to consider any other factors or it is just straight forward substituition into the summation equation and calculate the unknown $\endgroup$ – Elvir Peco Dec 11 '20 at 21:27

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