[ntp:questions] Raspberry Pi error in PPM offset

unruh unruh at invalid.ca
Sat Aug 24 15:41:30 UTC 2013

On 2013-08-24, james.peroulas at gmail.com <james.peroulas at gmail.com> wrote:
> On Friday, August 23, 2013 10:55:06 AM UTC-5, David Woolley wrote:
>> Unless ntpd is failing to converge to an average offset of zero 
> It's converging to an average time offset of zero, but an average frequency offset of +2.5PPM.

Fine. That means that your RPi crystal oscillator is 2.5PPM out from
spec, or the calibration that the operating system did on the crystal to
set the clock rate is 2.5PPM out. Either way ntpd corrects that error.
If it is the calibration loop, then probably the next time you boot up
it will be -4.7PPM out. etc. 
man adjtimex
Especially the tick value and the frequency.
You also still have not told us how you made your measurements.

>> (accounting for signs), the question is of marginal academic interest.
> So, are you saying that the PPM value returned by NTP is to be ignored, is purely for information purposes, and is not to be interpreted as having any real-world meaning?
> James

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