[time-nuts] Looking for RTC or some combination of MPU/crystal for 0.1ppm accuracy.
hmurray at megapathdsl.net
Sat Sep 12 21:55:42 UTC 2009
rickharold at gmail.com said:
> I need to find a solution for a RTC which provides 0.1 ppm accuracy in
> the form of a RTC/MPU or some other combination, oscillator etc.. I'm
> creating some sensors which all need to do timed measurements and need
> to be at the same time. They can get a time beacon every 10 seconds
> but then need to accurately perform independently 20x / sec. They
> cannot communicate with each other and other than the time beacon are
> unconnected. After a period of time they will send their time-stamped
> data out.
What do you mean by "0.1 ppm accuracy"? I'm assuming you mean over
How accurate is your beacon? What sort of accuracy do you need?
Assuming that you don't have wild temperature swings...
Just calibrate whatever crystal you would normally use. It will be off by
many ppm, but at the ppm level, it's stable at a given temperature. Using
your 10 second beacons, you can measure the actual frequency and correct in
software. It will change with temperature, but that will be slow enough so
you can track it.
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