On Feb 12, 2015, at 4:02 PM, William Unruh <un...@invalid.ca> wrote: >> You're describing a TCXO; using a temperature sensor to compensate for >> thermal >> drift would gain perhaps a factor of 5 accuracy. > > No, that is a hardware solution. There are software solutions-- a > termistor to meaure the temperature of the crystal ( or somethign > nearby) which feeds that measurement to the OS. the revised ntp then > reads the temperature, and corrects the drift rate as a function of that > temperature.
Anything which measures temperature to provide a compensation for XO frequency is a "TCXO" which is an acronym for "Temperature Compensated Crystal Oscillator". There are details which matter; see: [1]. > This is all without controlling the temperature of the oscillator (TCXO) > but rather measuring that temperature-- much cheaper. Something which controls the temperature of the oscillator is an OCXO, which is an "Oven Controlled Crystal Oscillator". Regards, -- -Chuck [1]: If you wanted to distinguish between a precalibrated analog feedback circuit commonly included within the package and external compensation via a digital temp sensor (perhaps located on the motherboard chipset) and a lookup table, ie, ATCXO vs DCXO, fine. Good definitions here: http://www.radio-electronics.com/info/data/crystals/tcxo.php The lookup mechanism described above would be adjusting the kernel's tick values (ie, how many ticks it counts per second) and not providing a voltage change-- aka VCXO-- to change the actual crystal oscillation frequency. _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions