[time-nuts] Measuring short term stability minus linear drift

Tom Van Baak tvb at LeapSecond.com
Sat Oct 8 00:49:13 EDT 2011


> I want to measure the short term stability of a source
> with substantial linear drift.  I would like some measure
> of stability along the lines of Allan deviation, but I
> only want to measure the "noise" and ignore the "drift".
> AFAIK, ADEV treats linear drift like a form of noise.
> Has this problem been solved before?
> Any ideas?
> 
> Rick Karlquist

Right, ADEV will suffer with linear drift.

Plot the frequency first to see how linear the drift is. If it
looks like you expect (that is, mostly a straight line) then
it's safe to remove it from the raw data with a quadratic
least squares fit. Then compute ADEV on the residuals.

Another way it to use HDEV on the raw data.

Let me know if you want the command line tools I use
for all this.

The other suggestion is to use John Miles' TimeLab.

/tvb





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