[time-nuts] Modified Allan Deviation and counter averaging

[Poul-Henning Kamp]

>> Shouldn't the quantization/ measurement noise power be easy to measure?

So I guess I havn't explained my idea well enough yet.

If you look at the attached plot there are four datasets.

"100Hz", "10Hz" and "1Hz" are the result of collecting TI measurements
at these rates.

As expected the X^(3/2) slope white PM noise is reduced by sqrt(10)
every time we increase the measurement frequency by a factor 10.

The "1Hz 10avg" dataset is where the HP5370 does 10 measurements
as fast as possible, once per second, and returns the average.

The key observation here is I get the same sqrt(10) improvement
without having to capture, store and process 10 times as many
datapoints.

Obviously I learn nothing about the Tau [0.1 ... 1.0] range, but
as you can see, that's not really a loss in this case.

*If* this method is valid, possibly conditioned on paying attention
to the counters STDDEV calculation...

and *If* we can get the turbo-5370 to give us an average of 5000
measurements once every second.

*Then* the PM noise curtain drops from 5e-11 to 7e-13 @ Tau=1s


Poul-Henning

PS: The above plot is made by processing a single 100 Hz raw data file
    which is ny "new" HP5065 against an GPSDO.

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