[time-nuts] Poor man's oven
csteinmetz at yandex.com
Mon Jun 5 18:38:25 EDT 2017
> Today all you need is a reliable way to measure the error
> between the crystals' current temperature and the set point.
That's all that's ever been needed. But it is devilishly difficult to
measure the actual quartz temperature, or even to find a good proxy that
is easier to measure.
There is a fair body of published research on these topics, including
Rick's (et al.) work on zero-gradient ovens.
Keep this in mind when someone says they are controlling the "oven
temperature" to 0.001C (or even 0.1C). They are measuring *something*,
and may even be holding whatever it is "constant" within fairly tight
tolerances. But they have no idea what the quartz temperature is, and
no way to know with precision the relationship between the measured
temperature and the actual quartz temperature.
Some years ago, I consulted for a research group that was using a number
of non-contact technologies to measure the temperature of oscillating
quartz crystals. The results were promising, but there were some issues
with measuring the temperature (which is, essentially, quantifying tiny
random molecular motions within the crystal lattice) against the
background of the hugely greater macro motion of the vibating quartz. I
never knew the final conclusions, nor am I aware of any systems designed
using these principles or methods. But it is something to think about
if you *really* want a temperature-stable oscillator.
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