[time-nuts] temperature sensor

[Attila Kinali]

On Mon, 21 Jul 2014 04:39:51 -0700
Alexander Pummer <alexpcs at ieee.org> wrote:

> NTC are not that very stable, they are amorphous material winch could 
> recrystallize slowly and therefore change it's electrical behavior , 
> PT100 style is more reliable since it is pure metal

How long is the time constant for NTCs?
I guess, it wouldn't matter for most of the measurements we do,
as NTCs need to be "calibrated" before precision measurements
anyways. Unless one measures over several months, or years.
But on this timescales, i wouldn't really trust an off the shelf
PT100 either. Not unless i measure its stability

For use in GPSDOs and OCXOs, i guess it doesn't really matter,
as long as the NTC stays within spec. There an external loop
corrects for the variation/drift of the measurement.


While we are at it: what is a good way to calibrate/characterize
temperature sensors that is available to hobbyists?

			Attila Kinali

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