[time-nuts] Rb as source for ADEV?

Tom Van Baak tvb at LeapSecond.com
Thu Feb 6 23:27:05 EST 2014


> Averaging time is unfortunate in several aspects, part for it not being 
> averaging being done and part for the fact that averaging is a separate 
> processing step that can be done, and you can make a plot orthogonal to 
> the ADEV plot with various degrees of averaging-pre-filter.

I agree.

> The MDEV uses a tau averaging for a tau observation time.
> 
> The tau is really the observation time, and ADEV is the frequency 
> stability for that observation time, that is the ROMS relative frequency 
> noise when observing it tau seconds later. Similarly the TDEV is the 
> time stability in RMS s for the observation time tau.

The phrase "observation time" is probably no better than "averaging time" for the x-axis label; they both give the impression of elapsed time to newcomers. Both "observation" and "averaging" connote run time or elapsed time or experiment duration. I would stay away from the word "time" on the ADEV x-axis completely. Using the word "interval" (as in "sampling interval") is good; the least likely to be confused with elapsed time. Also, it's always nice to add "tau" to the axis label since that letter is universally associated with sampling in T&F metrology.

Stable32 uses "Averaging Time, tau, Seconds". TimeLab avoids the issue by not having labels.

/tvb




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