[time-nuts] Poor man's oven
csteinmetz at yandex.com
Tue Jun 6 11:55:23 EDT 2017
>> what I'm interested in is at which exterior temperature
>> OCXO ovens work best ?
> Here's my guess...
> 1) you want minimal gradients across the device for a variety of reasons
> 2) therefore you want least amount of heat from the heater
> 3) therefore somewhat below the setpoint of the heater.
It depends on what you mean by "best." "Best" can mean "minimizes the
wander in oven-regulated temperature at a constant (or slowly-changing)
ambient temperature," or it can mean "fastest recovery when the ambient
temperature changes more rapidly."
Minimum heater power tends to favor the first, but be careful -- this
means a low *available* (maximum) power, not just using a high-powered
heater at a lower output. This is because the rate of temperature
change for full-scale heater swings is proportional to maximum heater
output, not to the ambient-to-oven differential, and this "granularity"
of the heater control function is what determines the oven wander at a
constant (or slowly-changing) ambient temperature.
A higher differential between the set point and ambient, and higher
maximum heater output, are necessary for fast recovery from larger
and/or faster changes in ambient temperature (i.e., to achieve a higher
Note that the above is why, for an oven controller with decent loop
gain, it is not necessary to control the ambient temperature very
tightly -- it is only necessary to slow down the *rate of change* in
ambient temperature to the point that the loop can track it to the
required tolerance. See previous list discussions of "cast aluminum
boxes" and "thermal capacitance."
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