Hmm, I'm not quite sure what you mean - you're comparing against a number of different sensors/types? If you aren't taking any absolute, calibrated measurments surely you can only conclude that some (perhaps most) drift at similar rates and any that don't stand out beause they are different - but those could be the ones that aren't drifting significantly?
Isn't this the problem of having lots of clocks or voltage references and never being sure which are right?
Hi
Not really:
You have a voltage reference, it is out in the ambient environment
You have a voltage controlled gizmo that you are compensating, it has a known sensitivity to the control voltage
You have a temperature sensor that gives you the data for the compensation process
You compensate the whole thing to a few 10's of ppt using the temperature data from the sensor
You validate the compensation process and put the beast on long term burn in
You come back in 3 months / 6 months / 12 months and see how everything is holding up
If the compensation holds to a few ppt or so of what it was, you can back into the stability of the parts.
The compensation of the device is a temp sensor driven process so the end result is the sum of all the errors along the way. You can put upper bounds on things, but not lower bounds. We have a few points in the system we can monitor and take out a couple things, it's still an "upper bound only" estimate.
Yes, there are a bunch of grubby details about sensitivity and how tightly you are compensating things vs how bad they were at the start. Since it's my employers "secret"
process,I can't get into quite everything. I suspect I've put enough in there that you can pretty well guess what we are playing with.
Bob