Clock accuracy in ppm

# Clock accuracy in ppm - Clock accuracy in ppm Crystal Clock...

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Clock accuracy in ppm Crystal Clock accuracy is defined in terms of ppm or parts per million and it gives a convenient way of comparing accuracies of different crystal specifications. . The following headings give practical calculations showing the typical errors you will encounter when using a clock of a specific type with a specific accuracy. How good is a 1% accurate clock ? If you look at a day's worth of timekeeping then you have 24 x 60 x 60 = 86400 seconds in a day. So the maximum error after a day has passed is 1% of 86400 = 864 seconds = 14 minutes! How good is a typical crystal ? A typical crystal has an error of 100ppm (ish) this translates as 100/10e6 or 0.001% (its the same number expressed as a percentage). So the total error on a day is 86400 x 0.01%= 8.64 seconds per day so in a month you would loose 30x8.64 = 4.32 minutes per month. How good is a watch crystal ? A watch crystal has an error of 20ppm (ish), but you have to design the board layout well, this translates as 20/10e6 (0.002%) which

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Clock accuracy in ppm - Clock accuracy in ppm Crystal Clock...

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