[time-nuts] Re: Timestamping counter techniques : phase computation question

[Erik Kaashoek]

Excellent questions.

The goal is to measure with a certain interval the phase of repetitive
events versus a clock.
The clock is assumed to be perfect. Also the counters are assumed to be
perfect.
The events can change their frequency and phase but any change within one
measurement interval is allowed to be averaged.
The measurement interval can be much larger than the period of the events,
this allows the measurement to make use of the many events for for one
measurement.

Practical example:
The clock is a 200MHz perfect clock.
The events come from an unknown quality XCO at 10 MHz
The measurement interval is 0.1 seconds
The goal is to derive the phase (and also the frequency) of the XCO versus
the clock from the counter data in the highest possible accuracy. Once this
is done the rest of the post processing of multiple measurements can be
done in tools like Timelab.
It would be extremely interesting if it is also possible to calculate a
"quality"  figure that quantifies the amount of deviation of the events
versus the presented measurement.
This would help someone looking at result of the measurement to understand
the real accuracy

And I am aware that as I don't know anything about this subject it seems
simple, and probably is not.
Erik.