Hi Alex,
Monitoring the temperature control loop of this OXCO is even easier
than that. Currently instaled is a HP10811. It has a very handy oven
monitor pin, that varies voltage with what the control does to keep
temperature constant. (Those HP guys were really thinking!) Any time
the oven has to react to something it's visible on that pin. Albeit,
most of the stuff is in the 100uV or under level, but it's there.
Currently there is a 8Ch 24bit DAQ card tied to this whole thing, and
the card has proven to be more than stable enough to see what's going
on. There is some correlation between the bulk supply voltage and
DAC/Phase, so the next step is to chase that down. Just not exaxtly
sure how it's getting in there. It's interesting what can be learned
from looking at a bunch of data...
The really interesting thing is what's going on with the GPS
temperature. You can see it ramp temp slowly, then drop 1/2 deg F, then
ramp up slowly, and drop again. One would guess that it's tied to CPU
load or similar. The only thing that bothers me about that, is the fact
that the GPS is very temp sensitive. It may very well be the limiting
factor. I have yet to monitor the VCC to the GPS, so there might be
something more to learn...
73,
Dan
>
> just thinking; OXCO is one ovenized crystal oscillator with temperature
> control, better to say temperature stabilizer, thus if the outside
> temperature changes the control loop shall keep the internal temperature
> constant-- by definition,
> the function of the temperature control loop could be observed by the
> variation of the supply current of the oven. Also the reference voltage
> supplied from inside of the OCXO is coming from a voltage source which
> has stabilized temperature, therefore it is "a relative stabil reference
> voltage source", which could be used to compare the stability of other
> voltages and thus, it could be found which voltage is moving with the
> environment's temperature.
> 73
> Alex
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