[time-nuts] frequency stabilty question

Tom Van Baak tvb at LeapSecond.com
Mon Aug 15 15:42:11 UTC 2011

> Is it correct to assume that if you collect data every 10 ms for
> 10 seconds (1000 data points in total), you could actually split
> that data set into 100 sets of data at 1 seconds for 10 seconds
> (10 data points in each set), which would have the same statistical
> quality (I am sure caveats would apply) as a single data set of
> 1000 data points collected at one second interval over a total
> period of 1,000 seconds?
> Didier KO4BB

If you look every 10 ms and collect data for 10 seconds you will
be able to make a log-log ADEV plot for points from 0.01 s to 2
seconds, no more, no less.

In order to plot ADEV points less than tau 0.01 s you need to
re-measure using an instrument that gives data faster than one
every 10 ms.

In order to plot ADEV points more than tau 2 seconds you simply
need to let the measurement run much longer than 10 seconds.
For example, if you measure for 4 or 5 hours then you can plot
ADEV out to 1 hour.

In other words, the leftmost point on any log-log ADEV plot is
determined by how *fast* you can collect data and the rightmost
point is determined by how *long* you collect data.


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