[ntp:questions] drift modeling question

Unruh unruh-spam at physics.ubc.ca
Sun Jul 13 06:08:51 UTC 2008


shy author <shy.author.not at aol.com> writes:

>> A Quadratic correction tends to run away pretty badly if you suddenly
>> have a period of no ntp readings. But I am not at all sure that is what
>> you mean. Rather you seem to mean that one use the temp to estimate what
>> the linear drift is ( from the past readings of temp and drift.)

>Correct, in that the linear correction will vary with temperature (and 
>could be matched closely by a quadratic)

That is NOT a quadratic correction. It is a linear correction where the
linear coefficient depends on temperature. 

>I am thinking of a least-squares fit to the drift data, versus 
>temperature.  Another poster mentioned that we really need temperature of 
>the crystal, I agree, but there should be strong correlation between that 
>(unknown) temperature and the motherboard or processor chip temperatures.

And a lag.




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