[time-nuts] Thought experiment on a low cost timing board

John Pettitt jpp at cloudview.com
Mon Feb 27 00:11:56 EST 2006

Hal Murray wrote:
>>  What prompted this in the first place was the horrible temperature
>> sensitivity my soekris boxes exhibit - I can only keep them to within
>> 10us of the gps 95% of the time and the occasional 100us excursion is
>> not uncommon.   I want to be stable to the limit of the gps I'm using
>> -  for no other reason than the belief that I can do it for way less
>> than  commercial devices using open source software and low cost
>> hardware.  In  other works I'm hacking for the sake of it :-) 
> Is there a temperature sensor on the Soekris box?  Is it located anywhere 
> near the crystal?
> Good read on that topic:
>   http://www.ijs.si/time/temp-compensation/
It runs out there is a temp sensor on the board - it only reads in one
degree C steps but if I take a 10 min rolling average of the temperature
I can fit the temp curve almost exactly to the ntp frequency
compensation (it's drifting by about  0.44 PPM per degree C).   I'm
going to hack some code into ntpd tomorrow and see if I can do the same
compensation as in the example above.


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