[time-nuts] Some More questions
cfharris at erols.com
Thu Jan 19 08:22:21 EST 2006
Poul-Henning Kamp wrote:
> In message <43CF2281.4000304 at erols.com>, Chuck Harris writes:
>> Didier Juges wrote:
>>> One problem with that approach is that crystals that are not intended
>>> for oven operation are optimized for minimum frequency change over 0-50
>>> or some other "normal" environment temperature range, and at 75 degree C
>>> or wherever you are going to run the oven at, the temperature
>>> sensitivity might be much greater than around 25 degrees. So even though
>>> the oven might reduce the temperature variation by a factor of 10 or
>>> better, the overall frequency sensitivity may not improve by the same
>> Of course, one could take a small Peltier device, and a resistance heater,
> Peltier elements work both ways so save the heater.
True, but there is an advantage in not passing through that
dead zone around zero where you transition from Peltier cooler
to Peltier heater.
If you want the best precision, you need to drive the Peltier
device so it provides enough cooling to bring your oven a few
degrees below the set point, and let the heater servo the oven
temperature up to the set point.
This is the way that precision environmental chambers work.
It would be interesting to see how such an oven performs compared
to the traditional double oven.
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