[time-nuts] 53230A weirdness
Ole Petter Ronningen
opronningen at gmail.com
Thu Nov 23 15:05:38 EST 2017
I've done some experiments on my 53230A, and I've come across an issue I
think could be worth knowing about.
I have not tested this on other 53230A's - if anyone has a 53230A and some
spare time, I'd be grateful if someone could try to replicate.
In a nutshell, the first frequency measurement following an INIT is biased.
The magnitude of the bias is dependant on measurement mode (CONT/RCON), and
It is worth noting that every READ implicitly calls INIT - so any software
collecting a time series using repeated calls to READ to fetch single
readings will give biased results. Not for the first sample in the series,
but all of them.
As an example, the last time series I collected this way using RCON and
0.1s gatetime gave an average frequency error of -5.2e-10.
A writeup is here: http://www.efos3.com/HPAK53230A-1.html
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