[time-nuts] 53230A weirdness
Ole Petter Ronningen
opronningen at gmail.com
Fri Nov 24 10:34:49 EST 2017
Although, as I read the paper again, it is possible that the frequency bias
in the 10 second CONT-mode measurements could come from this effect.
That particular series (and only that) was collected using TimeLab. I
supplied them with a custom compiled driver that does not use repeated
calls to READ - and therefore does not exhibit this particular bias. I
always assumed that this driver was used to collect that series, but the
paper does not state this explicitly so I might be wrong.
The bias I am pointing to is gate time dependant, the bias getting smaller
with longer gate times. It is possible it will be at the E-15 level at 10
second gatetime, like in the paper.
On Fri, Nov 24, 2017 at 2:45 PM, Magnus Danielson <
magnus at rubidium.dyndns.org> wrote:
> Is this part of the behavior that the Norwegian NMI was presenting at a
> poster session at EFTF 2016 in York?
> I remember they borrowed your 53230A for that work.
> On 11/23/2017 09:05 PM, Ole Petter Ronningen wrote:
>> Hi, all
>> 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
>> The magnitude of the bias is dependant on measurement mode (CONT/RCON),
>> gate time.
>> 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
>> Best regards,
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