[time-nuts] AVAR calculation

Magnus Danielson magnus at rubidium.dyndns.org
Tue Jan 12 00:41:54 UTC 2010


Filip Ozimek wrote:
> I'm trying to calculate AVAR from collected data, but I would expect a different behavior of my DUT. Does anybody can calculate the AVAR for me?
> Gate time was 1s, without any deadtime between measurements,
> this is a file http://www.fuw.edu.pl/~fozimek/pomiar61-frep.txt
> with collected data.

Would you care to elaborate on how this data was collected?

By the looks of things, if this is indeed frequency data, then it is 
interesting to note that data is in steps of 1/4000 Hz every second. For 
a 250 MHz oscillator having 4 ns period time, this amounts to a time 
resolution of 1 ps. A quick histogram displays that 115 bins is filled 
in what looks like Gaussian-like... but it is dragged out by the drift.

Few counters give such numbers, so I am curious. There are ways to 
improve frequency measures, but they tend to smooth over data in a 
fashion that you don't want for normal ADEV analysis. At the first look 
on the data, the source looks very quiet. The ADEV curves plotted looks 
more normal.

Cheers,
Magnus



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