Resolution of F vs t measurement

by Excom
Tags: measurement, resolution
Excom is offline
Jan30-12, 10:20 AM
P: 44
Hi all

I have measured the resonance frequency of a resonator as a function of time by mean of a Laser-Doppler vibrometer and a frequency counter. In this measurement there are some fluctuations in the measured frequency as time goes by.
My question is: How do I determine the resolution of this frequency measurement? Or in another way: How precise can I resolve the frequency? Do I take the standard deviation for a period and then define this as my frequency resolution?

I hope someone can help me.

Best regards
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sophiecentaur is offline
Jan30-12, 11:27 AM
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That would be the RMS error. A pretty universal way of stating errors - I say go for it.
Excom is offline
Feb1-12, 07:13 AM
P: 44

Excom is offline
May19-13, 11:24 PM
P: 44

Resolution of F vs t measurement

A more correct way of doing it is to calculate the Allan deviation as a function of integration time and then take the minimum value.
f95toli is online now
May20-13, 04:33 AM
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Indeed. the standard deviation is not a good measure in these situations. The reason is that it only converges for white noise, for all other noise types the STD will give you the "wrong" result which is why the Allen deviation should always be used for this type of analysis.

Have a look at the NIST handbook of frequency analysis (free download). Also, there are free Matlab routines for calculating the ADEV available on Mathworks file exchange.

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