On 07/02/14 04:31, Tom Van Baak wrote:
Hi Tom,
If I understand you right, the only thing I need from the adev program is the
OADEV values and those are the new
ADEV? Here's the plot for the past 24 hours using "0" for bins. It takes a few
seconds to run, doesn't it?
Yes, just grab the code for calc_adev() in
http://leapsecond.com/tools/adev_lib.c and always set ovlp = 1. Either way,
it's ADEV; it's just that the overlap method gives better results (smaller
error bars).
http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/ADEV.2.6.png
Suggestion: do not label the x-axis "time in seconds". This gives the impression that the axis is some sort of elapsed time.
Better wording might be "integration time", or "sampling interval", or "averaging time", or "tau",
or "sampling interval, tau".
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.
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 RMS relative frequency
noise when observing it tau seconds later. Similarly the TDEV is the
time stability in RMS s for the observation time tau.
ADEV also rises for long taus on oscillators, where you expect even
better averaging to keep it going further down.
The field is confused enough, so I want to avoid this confusion.
Cheers,
Magnus
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
