[time-nuts] Crystal aging
Richard (Rick) Karlquist
richard at karlquist.com
Thu Sep 3 15:46:43 UTC 2009
> Maybe! But for the sake of clarity: I have been asking how HP/Symmetricom
> manage to handle the regulation loop appearantly WITHOUT time constant
> adaption/switching and with a fixed time constant that seems to be much too
> high to start with for a cold OCXO.
> Best regards
> Ulrich Bangert
One answer might be the use of a second integrator. The HP5061 used
an analog second integrator, which was quite non trivial to implement
at the time. The 5071 also uses a second integrator, which is of
course digital. The oven control loop of the E1938A uses first and
second integrators (PID + I^2) to get the best of both worlds.
None of these use switched time constants.
Rick Karlquist N6RK
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