[time-nuts] Crystal aging

Ulrich Bangert df6jb at ulrich-bangert.de
Fri Sep 4 07:05:29 UTC 2009


while the discussion was about the frequency control loops of GPSDOs and not
the temperature control loops of their OCXOs your answer applies as well to
what I have been asking. That was what I thought of when I talked about "3rd
ore more order plls". 

Best regards
Ulrich Bangert

> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Richard 
> (Rick) Karlquist
> Gesendet: Donnerstag, 3. September 2009 17:47
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] Crystal aging
> > 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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