Chris wrote:
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.
Best regards, Charles _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
