Standard set of terms for precision, accuracy, related concepts.

Kurt Roeckx kurt at
Mon Apr 24 17:30:03 UTC 2017

On Mon, Apr 24, 2017 at 10:07:47AM -0700, Gary E. Miller wrote:
> frequency offset:
>     The difference between the ntpd calculated frequency and the local system clock frequency (usually in parts per million, ppm)
> jitter, dispersion:
>     The short term change in a value

For me jitter is about chances in the interval. Some examples which
I think are relevant are:
- For a PPS signal, the signal generated by the source is not
  exactly 1 second each time, but on average it's 1 second.
- For the same PPS signal, there is a variable delay between
  the source generating the edge and the PC having seen it
  and measured the time.
- A packet send over a network doesn't always have the same delay.

dispersion for me is the standard deviation


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