I finally have a need to ask a question about time measurement! I want to measure the accuracy of a 1Hz signal from a real time clock (RTC) chip with an integrated TXCO allegedly good for +/- 2ppm accuracy. My employer is too tight to buy a good frequency counter, but I do have a GPS module outputting 1PPS. If I use a little micro running at 16MHz from a jellybean crystal to measure the period of the 1PPS signal from the GPS concurrently with measuring the period of my test signal, will I be able to get accuracy of sub ppm? My resolution for a single period is 62.5 ppb, but this is a lot different to accuracy. I could easily count multiple periods, as I do not need fast results. My thought is that the 16MHz will have jitter and a pronounced drift, but that as the measurements of my reference and signal are done nearly concurrently, the errors will be very small.
The need for this is that the RTC chip for a product has the engaging property of shifting it's frequency by several ppm after being soldered to the board, and I need to characterise this to get accurate timing for the product. -- Tom Harris <celephi...@gmail.com> _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.