[ntp:questions] Re: HowTo calibrate system clock frequency using NTP
daniel.kabs at gmx.de
Thu Feb 2 09:34:38 UTC 2006
Terje Mathisen wrote:
> This is well within the expected precision for such an experiment, the
> final ntp.drift value (23.2 or 268.3) probably reflects the current
> drift rate, not the average.
> These two values are different because the environmental temperature
> varies, often diurnally, so if you log the changes in ntp.drift then
> you'll probably notice that the average corresponds closely to the
> 23.7/23.8 numbers.
Did I understand you correctly: You are insinuating that least-squares
fitting the time offset is getting an average value whereas the
frequency error (ntp.drift value) represents a "live" value.
I expected it to be the other way round: I thought the frequency error
is a "slow" value that takes hours or days to converge as a result of
the control loop phasing in and as such can only slowly react to
environmental changes (e.g. change in temperature). This contrasts to
measuring the time offset over a short periode which gives a "snapshot"
of the current clock drift and as such represents current environmental
What am I getting wrong here?
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