[time-nuts] Thermal Compensation: Digital vs Analog

Chris Albertson albertson.chris at gmail.com
Wed Feb 26 13:26:26 EST 2014

If you can understand the temperature effects and can model them
accurately and you can measure temperatures and your DAC steps are
small enough, then digital compensation can be "perfect".   But you
are unlikely to meet all those conditions.  In theory if the problem
is that the voltage diver's ratio is a function of temperature then
you can epoxy the LM34 to the divider and adjust the output of the DAC
based on the current divider ratio.   But in the real word you don't
know the exact function or temperature and the DAC might have larger
steps.     I think the best plan is to reduce the source of the error,
(the analog fix)  Then if there is still any error source you can
measure and model to that too.

On Wed, Feb 26, 2014 at 8:09 AM, Bob Stewart <bob at evoria.net> wrote:
> I've been experimenting with digital thermal compensation on my GPSDO.  The results have been favorable for a 14 bit dithered PWM-based DAC, but leaves a bit to be desired in the big picture.  And it takes up a lot of program bytes on my PIC..  What's the general consensus on this?  Should thermal compensation be completely analog?
> Bob - AE6RV
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Chris Albertson
Redondo Beach, California

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