[ntp:questions] Re: Reading time offset from ntp variables using ntpq

Daniel Kabs daniel.kabs at gmx.de
Fri Feb 17 09:43:25 UTC 2006


Hello Professor Mills!

Apropos engineers: any engineer strives for high precision measurements 
and thus tries to minimize uncertainty to a reasonable level. So for any 
method of measurement the magnitude of uncertainty has to be determined 
and valued. That's what I am trying to do currently :-)

Enter Plan B: You suggested to "record the time of day and the offset", 
without saying how you'd record the time. So I tried different methods 
(for "recoding the time") and found

cron   :  23.40 s = 270.83 PPM
reftime:  23.35 s = 270.25 PPM
org    :  23.30 s = 269.67 PPM
rec    :  23.29 s = 269.56 PPM

Mh, maybe I should have converted the values to PPMs earlier! They look 
much nicer now. Leaving out the "cron job", they agree within +/- 0.5 
PPM. Of course, this should be backed by repeating the "experiment" and 
checking how the values scatter (disperse? I'm don't know the proper 
English word here).

You are right, this uncertainty is reasonable. So I should stop bugging 
you about timestamps :-)

Mission accomplished! Thanks.
Bye now,
Daniel

David L. Mills wrote:
> Daniel,
> 
> Have you considered what an engineer means by "almost exact?" There is 
> always an uncertainty in any physical measurement. Yours is no exception.




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