Thank you robrenz,
saturation are you one of the participants of this topic over there (time nuts)?
Bingo, the 6680 is a very capable timer, 250ps single shot,
should be nice for interval measurements, you are well equipped for time
measurements with that and the Thunderbolt.
The schematic is the logic part of this circuit, the output is OUTD pin:
Measuring this OCXO for the first time I was feeling the real accuracy
and stability of an average Rb oscillator. So I tried to make a a comparison:
I used the same setup with an Rb, it's period error was around -1x10^-11,
the period error variation is less than 10^-16 per second -> less
than 1x10^-12 per day, but buried in the noise, so these data are
not really accurate. (See second attachment below).
The funny thing it that the Rb was powered form cold immediately
before the start of the graph, the frequency error could be trimmed
out by the serial interface interface, but my Rb has no
thermostabilization yet, so nothing to gain.
The abrupt frequency variation at 90000s reflects an internal
DDS frequency variation, probably due to some temperature
compensation, I'm still figuring out this aspect.
That's all, for now