I'm looking at various types of oscillators and they all have a certain amount of error. Furthermore, that error can increase with various external conditions.
If I'm using these clocks for precision time references, how do I calculate exactly how much drift I have.
Let me take a stab at it and tell me how far off I am.
Let's say I'm using the DS32KHZSN. A temperature compensated 32.768kHz external oscillator rated for use between -40 to 85 C.
This chip says it's rated between -7.5 and 7.5 ppm stability. So in other words, for every 1 million 'ticks' it could be +/- 7.5 ticks off the real time.
1 million ticks = 30.517578125 sec +/- 0.006984919309 sec
so by a little multiplying...
1 day = 2831155200 ticks = 86400 sec +/- 6.48 sec
1 year = 365 days +/- 39.42 minutes
Is my thinking and math right here?
It seems like to have a very very accurate time keeping system that doesn't have drift you have to use a much more expensive clock.
Some other timing chips that I pulled off digikey...
Connor Winfield D75AS-020.0M | $31.50 | .25PPM | +/- 21.6ms/day
Maxim DS32KHz | $7.42 | 2PPM | +/- 172.8ms/day
Abracon Corp AOCJY-10.000MHZ-E | $168.84 | 10PPB = .01PPM | +/- 864us/day
Abracon Corp AOCJY-20.000MHZ | $168.84 | 5PPB = .005PPM | +/- 432us/day