[ntp:questions] drift modeling question

Uwe Klein uwe_klein_habertwedt at t-online.de
Sun Jul 13 09:12:27 UTC 2008


shy author wrote:
>>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)
> 
> 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.
> 
One could stick a LM75 Temp Sensor ( or similar with better resolution )
to the Xtal and connect it to the MotherBoard SM-Bus.
Should not be all that difficult to integrate.

uwe




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