[time-nuts] ADEV query Timelab and TICC
Tom Van Baak
tvb at LeapSecond.com
Sun Mar 19 15:57:07 EDT 2017
> I'm probably missing something obvious but don't understand what's
> happened here so any suggestions would be welcome.
Your setup sounds fine. Off-list, send me the TIM files and I'll see what happened.
I know we all love ADEV but in general always look at the phase, phase residual, and frequency plots first before you bother with ADEV. These strip chart plots better show your raw data and measurement. Even a single glitch will be visible. Only if these plots are "clean" should you go ahead and use ADEV. Another trick is using the TimeLab "Trace" feature which splits the data into N segments and computes ADEV for each one independently.
But in this particular case where you are comparing two GPSDO a phase difference plot will likely be more informative than an ADEV plot anyway. You may also want to play around with the averaging value (command 'g').
----- Original Message -----
From: "GandalfG8--- via time-nuts" <time-nuts at febo.com>
To: <time-nuts at febo.com>
Sent: Sunday, March 19, 2017 9:08 AM
Subject: [time-nuts] ADEV query Timelab and TICC
> Yesterday I used one of John's excellent TICC modules for the first time
> and initially set up a quick test using the 10MHz output from a Thunderbolt
> as the frequency reference to measure the 1PPS from an Oscilloquartz Star4
> GPSDO, with the TICC output feeding a USB3 port on a Windows 10 PC running
> the 64 bit version of Timelab 1.29.
> I'll attach a copy of the test plots I'm referring to but just in case
> this doesn't get through I've also uploaded it to....
> Using the basic settings as described in the TICC manual the first run was
> for 1 hour and seemed fine so I decided to extend the run time to 6 hours.
> The first 6 hour test started to follow the 1 hour plot as expected and I
> watched this on and off and can confirm it did so up to somewhere between
> the 100s and 1000s points on the x-axis, but some time after that the
> complete plot shifted upwards and then continued to completion to produce the
> magenta trace.
> I wasn't watching when it shifted so don't know if it was a jump or a
> gradual shift but did see it continue until completion. When I repeated the 6
> hour test, again without changing anything, and hoping to observe the effect
> as it happened, it produced the green trace which was what I'd been
> expecting to start with. Since then I've made other test runs and again all seems
> to be as expected.
> Throughout the tests I have been simultaneously streaming data from the
> Star4 to Lady Heather via a "proper" serial port on the same PC so did wonder
> if there might be some form of data conflict but it doesn't seem to have
> shown up as any obvious form of corruption and hasn't repeated itself.
> Nigel, GM8PZR
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