On Jun 6, 2017, at 7:10 PM, Chris Albertson <albertson.ch...@gmail.com> wrote:
There are more sophisticated control loop designs that can handle this
better, eg by using two temperature sensors, one at the crystal and
one at the heater. But designing them correctly is more difficult
than the normal PID loop.
In the E1938A oscillator, we used a PIDI^2 loop. IOW, a PID
plus a double integrator. This was Len Cutler's idea.
Once the constants were dialed in, this worked phenomenally
well in terms of transient response. Even dumping in liquid
nitrogen full throttle into the environmental test chamber
barely wiggled the crystal temperature/frequency.
Rick N6RK
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