[time-nuts] quartz drift rates, linear or log
Tom Van Baak
tvb at LeapSecond.com
Sun Nov 13 09:56:31 EST 2016
>> http://leapsecond.com/pages/tbolt/TBolt-10day-fit1-e10.gif
> Hi Tom,
>
> Fascinating when you've done that linear fit - many of the plots now look very similar,
> suggesting environmental conditions? From that it would now be nice to log temperature,
> pressure, humidity, (& mains voltage?), and see if there is any correlation there.
>
> Wonderful to see plots of such a large group - well done!
>
> Peter
That's correct. Yes, I am also logging environmental parameters. Stay tuned for that. Also, you may have noticed the "thermal events" that I deliberately caused in the lab once in a while to make environmental correlations more obvious.
The end goal is not only to extract the approximate tempco of each unit through correlation but also to post-process the data to partially back out the temperature component and produce a set of second residual plots. So you go from raw data, to measuring drift, to removing drift, to measuring tempco, to removing tempco. At this point you get closer to revealing the intrinsic performance of the oscillator.
I did the same for "Clock B" last year:
http://leapsecond.com/pend/clockb/2015-tvb-Greenwich-ClockB-ppt.pdf
http://leapsecond.com/pend/clockb/
In fact you don't really need to go through the plotting and fitting steps. There are standard techniques to fit N-dimensional models to data. So a frequency and temperature time series goes in -- and best fit linear drift and temperature coefficient estimates comes out. This will be automated, but for now I like the plots because they are more educational. Also the eye is extremely good at spotting interesting or unforeseen things that math and statistics are blind to.
/tvb
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