[time-nuts] Digital temperature compensation

Hal Murray hmurray at megapathdsl.net
Sat Nov 1 19:03:10 EDT 2014

dan-timenuts at drown.org said:
> I'm experimenting with using a temperature sensor to estimate local
> oscillator frequency changes.  My goal is to have a decent holdover clock
> for a NTP server with not so great GPS antenna placement. 

This is for ntpd rather than chrony, but it's a good read:
  NTP temperature compensation

> With the colder temperatures, there's a sudden drop off in frequency  that
> I'm having a hard time finding a equation that fits as nicely.    

That section of the graph doesn't make sense to me.  I suspect a glitch in 
your setup.

When does your GPS unit run out of satellites?

Where is your temperature probe?  Is it in contact with the crystal inside 
the PC?  Is the PC doing anything?  In particular at the times when the data 
doesn't make sense?

PCs can do a lot of self heating.  Try running a big workload when the 
temperature is in the middle of the good range.

These are my opinions.  I hate spam.

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