[time-nuts] uncertainty calculations

Hal Murray hmurray at megapathdsl.net
Sun Apr 16 00:46:22 EDT 2017

time at radio.sent.com said:
> * You might have any possible phase relationship between the two
>   signals. If they are exactly related by a 10^7 ratio, it's possible
>   for the 1 PPS edges to exactly coincide with the 10 MHz edges.
>   Depending on the type of gating circuit, you will have jitter and
>   possibly metastability resolving whether which edge occured first. ...

> * To stay away from such problems, most precision counters add a small
>   amount of controlled jitter (phase modulation) to the clock.  ...

My experience with metastability is that it's really hard to make it happen.

Are the clock and data in a good lab setup really stable enough to make 
metastability a problem?

How much does the added jitter screw up measurements where it isn't needed?

These are my opinions.  I hate spam.

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