On 07/02/14 05:27, Tom Van Baak wrote:
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.
Observation time is better, but it needs to be used properly not to be
confused with measurement time. You can never make a single term become
completely unambiguous from all interpretations, rather you pick one and
define what it means and stick with it.
Observation period is what I've used in the ADEV wiki. Avoids "time" as
it is often confused for elapsed measurement time.
Stable32 and SP 1065 (both by W. Riley) uses the loose term Averaging
time, as that is what it was called initially, before the analysis
became more complex and they needed to separate terms.
Cheers,
Magnus
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