RTC Calibration program

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ijabbott
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Re: RTC Calibration program

Post by ijabbott » Thu Sep 05, 2019 10:33 pm

mcc wrote:
Thu Sep 05, 2019 4:54 pm
For me it is not totally clear from the instruction, whether I have to set the clock each time I do the calibration...
You just need to know how much it has lost or gained since the last calibration, and the date of the last calibration (assuming the current date set on the calculator is correct), and the previous calibration value. I find the easiest way to do that is to set the clock each time, and use the timestamp of the RTCCALIB.CFG file itself to record when it was last calibrated.

Mine has gained an additional 3 seconds in the 29 days since my previous calibration, which is about 1 ppm. So I should probably subtract 1 from my current calibration value and reset the time. I didn't bother with the program to determine this minor adjustment.

Thomas Okken
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Re: RTC Calibration program

Post by Thomas Okken » Sun Oct 06, 2019 11:12 pm

I used the calibration program, and the results are excellent:

I synchronized my DM42 with time.gov at 7:05:00 PM EDT 2019-09-01

19 days later, at 10:24:00 PM EDT 2019-09-20, it was 67 seconds fast

The CALIB program returned value -43; clock re-synchronized

Now, another 16 days later, the clock is slow by less than 1/2 second. That's equivalent to about 10 seconds per year. I could wait a few months for the drift to build up to where I can do a second calibration step, but I don't think I'll bother. :D

grsbanks
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Re: RTC Calibration program

Post by grsbanks » Mon Oct 07, 2019 10:41 am

Thomas Okken wrote:
Sun Oct 06, 2019 11:12 pm
Now, another 16 days later, the clock is slow by less than 1/2 second. That's equivalent to about 10 seconds per year. I could wait a few months for the drift to build up to where I can do a second calibration step, but I don't think I'll bother. :D
The resolution of the correction is probably lower than that anwyay. I.e. if you alter the calibration value by even 1, it'll probably gain over a second in 16 days and end up a bit further out in the opposite direction to the error in there now.
Not SwissMicros staff, just an enthusiast.

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