How accurate is ClockCard?
The precision of the ClockCard is entirely dependent on the quality of the oscillator circuit. There are three sources of error in the oscillator: (1) calibration error, (2) temperature stability, and (3) aging. Understanding these will allow you to estimate the precision of the ClockCard in your application. For simplicity we will measure error in terms of PPM (parts per million). The unit PPM provides a number similar to error expressed with percentages, but reduces the number of decimal places required. For example, 0.001% converts to 0.00001which is equivalent to 10 PPM. Using the PPM notation makes it easier to deal with very small deviations. The PPM terminology is also useful for calculating ClockCard error in terms of seconds per month. Since an average month has approximately 2.63 million seconds, if the ClockCard error was 2 PPM, then total error for the month would be 2 x 2.63 = 5.26 seconds. Calibration error: The ClockCard oscillator is calibrated at the factory to within
