[time-nuts] temperature sensor

Attila Kinali attila at kinali.ch
Sat Jul 19 07:45:41 EDT 2014


On Wed, 25 Jun 2014 14:21:49 +0200
"Bernd Neubig" <BNeubig at t-online.de> wrote:

> the time-nut approach for temperature measurement would be to use
> a temperature sensor crystal - like the good old Hewlett-Packard guys 
>did many years ago. If you do not look for ultra-linearity of the frequency
> vs. temp response, there are several possible types of crystal cuts
> possible. The simplest one is the Y-cut or the slightly rotated Y+5° cut,
> which has a slope of about 90 to 95 ppm/K @ room temperature.
> Smaller sensor crystals are tuning-fork type crystals, which 
> come in the same small cylindrical package as normal watch crystals.
> For further reading I have attached an application note for such a
> crystal from AXTAL.

Do you have any data on the temperature resistance from case to crystal?
The PT100 and NTC sensors have the nice property of having a very good
thermal coupling between the sensor element and the case. But i suspect
that temperature sensor crystals have a very small area that couples
the crystal to the case (in order to get a high enough Q for the oscillator
to work), which in turn limits the speed at which the sensor reacts to
temperature changes.

				Attila Kinali

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