I’m thinking of making a clock (which would always be subject only to room temperature) using a 32.768 kHz xtal driving a counter. The xtal has 20 ppm frequency tolerance which I interpret as meaning my clock could be off by as much as (20/1,000,000) x (seconds in a year) seconds/year = 10 minutes and 30 seconds per year. If I measure my specific crystal’s deviation from the nominal frequency, to seven digits of precision (100 times better than 20/1,000,000), and use the difference as a correction factor in my code, will I achieve a corresponding increase in accuracy? What affects the frequency more, or even as much as, temp and age (an order of magnitude smaller effect than temperature, but I could correct for that, too, if necessary)? Anything else I’m missing? Thanks.
Joined: Tue. Apr 1, 2003
Posts: 480 View posts