Charles Swiger wrote:
On Feb 12, 2015, at 1:56 AM, Rob <nom...@example.com> wrote:
However, what I observe is that the plots of the offset show the derivative
of the environment temperature, which unfortunately cannot be controlled
any better. I am considering to locate the crystal that is responsible
for the timing and see if it could be ovenized or replaced by a more
I've considered packing some insulation around the crystal, this would
tend to stabilize (while also increasing) the temperature, but this
would also be likely to reduce its lifetime, and the motherboard would
probably conduct heat too well.
temperature-stable oscillator. However, one can argue that it could be
fixed in software as well. ntpd could sense a changing drift and extrapolate
it, if necessary helped by input from a temperature sensor.
You're describing a TCXO; using a temperature sensor to compensate for thermal
drift would gain perhaps a factor of 5 accuracy.
It should be noted that this experiment has been tried out in real life
a few times: It has always helped! Depending upon the (temperature)
offset between the selected sensor and the crystal, you can see an order
of magnitude improvement.
We don't have any code like that in the ntpd reference code base, simply
because it would be _very_ unportable. :-(
Terje
--
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
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