[time-nuts] Allan Deviation Calulations
michael.cook at sfr.fr
Thu Sep 22 11:00:11 UTC 2011
Le 22/09/2011 12:35, Martyn Smith a écrit :
> I'm trying to measure the Allan Deviation of an amplifier and need
> help with
> the maths.
> My measurement process uses the SR620 in time interval mode and I make
> measurement per second for about a day.
> I then use Ulrichs excellent plotter to calculate the Allan Deviation.
> The Allan Dev floor noise of the SR620 (without my amplifier) is as
> 9.91E-13 (1 second)
> 1.59 E-13 (10 sec)
> 3.00 E-14 (100 sec)
> I then add my amplifier into the measurement process. I get the
> Allan Dev results
> 1.09E-12 (1 sec)
> 2.48E-13 (10 sec)
> 4.32E-14 (100 sec).
> So the 1 sec Allan dev with my amp included, has gone up by 9.9E-14
> for the
> 1 sec measurement.
> How to I calculate the actual Allan Dev of my amp for the 1 sec period?
> Best Regards
I have always thought of a noise floor as the lower limit to which you
can trust your measurement. Measurements below the floor can be
statistically derived IIRC, but calculating the Allan deviation of it
makes no sense to me. As your measurements are all above it , you can
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