[ntp:questions] Re: HowTo calibrate system clock frequency using NTP

Hal Murray hmurray at suespammers.org
Fri Feb 3 10:44:35 UTC 2006


>I want to calibrate the system clock on a number of embedded systems. To 
>measure the frequeny error, I'm looking for a method that only takes a 
>few hours.

>I'd prefer to use the frequency value that ntpd writes into the drift 
>file but my test (see URL above) showed too slow a convergence. I have 
>to add, I ran the test without the "iburst" server option so updating to 
>a new ntpd version that supports "iburst" will speed things up.

What sort of accuracy are you expecting?

The main contribution to changes in drift is temperature.

Does your environment have a stable temperature?

Are you calibrating your systems in the same location that
you will be running them in?  (Or calibrating them on a test
bench and shipping them to a customer?)

If there is any significant daily temperature changes, you will
probably have to calibrate over a day or several.  You might be
able to work out a procedure to calibrate your calibration procedure
to account for the current temperature.

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