[time-nuts] AVAR calculation

[Magnus Danielson]

Magnus Danielson wrote:
> 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.

Second thought, look at the tau=1 to 10 s and you see that it first 
rises before the usual slope. This is the effect of averaging in the 
counter. I would suspect that a HP53132A is being used.

Cheers,
Magnus