Poul-Henning wrote:
what I'm interested in is at which exterior temperature OCXO ovens work best ?
Jim replied:
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 dTemp/dTime).
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."
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.
