September update - clock accuracy

A project log for Low Power Environment Monitor / Logger

A small board that measures temperature, humidity and pressure every hour for five years.

alnwlsnalnwlsn 09/22/2018 at 17:081 Comment

I've been running this one board since mid-August, but since the beginning of this month I have not removed the batteries or set the clock, which marks the longest time so far that the system has been running continuously. I downloaded the recorded data and found it contains not a single error. However, I noticed a discrepancy today between my board and my other clock, of just over a second (the board is set up to take a measurement every minute on the minute, and will blink the green light as an indication). The DS3232M's datasheet specifies an accuracy of 5 PPM, so one second over this timeframe is well within spec. However, tuning in to WWV on the radio revealed that the board was dead on accurate; it was the Nixie clock that had drifted. The Nixie clock uses one of those counterfeit DS3231 modules from China as it's clock source. While the discrepancy is within spec, it is still the genuine Maxim chip in the logger board that has proved to be more accurate.


Jan wrote 09/22/2018 at 17:33 point

Yeah, the genuine DS3231M chips really are accurate. Use them all the time. I set them over serial on my PC, while having a TAB open with the atomic time. That way you can do long-term tests and see how accurate your gear is.

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