[time-nuts] What is "accuracy"? (newbie timenut, hi folks!)

Hal Murray hmurray at megapathdsl.net
Fri May 6 00:51:21 EDT 2016


catgirl at bordernet.com.au said:
> What I am trying to understand is, what does it REALLY mean when the
> manufacturer's specs for a frequency standard or 'clock' claim a certain
> accuracy. For ease and argument's sake let us assume that the accuracy is
> given as 100 ppm or 1e-4 ....   
...
> But does that mean that, say, after one day I can be certain that my clock
> will be fast/slow by no more than 8.64 seconds or could it potentially be
> greater than that?  ...

You have to read the data sheet, including the fine print.

For low-cost oscillator packages, there is a simple spec like "50 ppm" that 
covers everything.  It will be within spec if your power supply and 
temperature are within specs.  It will still be within spec after N years, 
but they usually don't specify that.

For expensive oscillators, the fine print gets interesting.  There are 
usually specs for aging rate and warm up time.

-- 
These are my opinions.  I hate spam.





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