[SOLVED] Understanding the math of ppm

[jpj]

I'm trying to understand the calculations used to arrive at 11.6ppm in the following statement:

There are 86400 seconds per 24-hour period, putting each second at about 11.6 millionths of the 24-hour period. That puts an error of 1 second per day at 11.6ppm.

Given a crystal with oscillator frequency of 32768 Hz and 86400 seconds per 24 hours, I'm trying to determine what formula arrives at 11.6ppm per second. I tried some different calculations but my math skills aren't great.

Thanks,
J

[Roberthh]

1/86400 ~ 0.000,011,6 = 11,6 millionth

[jpj]

Thanks Robert. But how did you know to use "0.000,011,6" to begin with?

I was trying to understand how 11.6 ppm was determined, given the other values were known.

[dhylands]

@roberthh showed that it came from 1 / 86400 which is 0.000011574 which is approx 0.0000116 or 11.6e-6

[jpj]

OK, that makes sense.

Thanks Robert and Dave!