[Openec] temperature sensor

[Frieder Ferlemann]

Hi Richard,

Richard A. Smith schrieb:
> > Frieder Ferlemann wrote:
> >
>> >> We need to know the beta of the NTC. It makes little sense to
> >
> > I've asked and I don't have it.  You will have to measure it.
> >
> > http://www.specsensors.com/ntc-engineering.asp
> >

thanks for the link.

> > We are not using 1% parts and have no model for what the self-heating is
> > so you are _still_ going to have to calibrate it if you want accuracy.

Of course no 1% parts. Yet a table based on the nominal value makes sense.

> > Steinhart-Hart is more accurate over a wider range than beta is anyway.
> >
>> >> invest time into inaccurately measuring the voltages at a subrange of the
>> >> temperature span while endangering the XO and still not being sure that this
>> >> sample would be representative.
> >
> > Endangering the XO?  Who told you that? We don't care about the

If I'd cool it down here, moisture would condense.

> > accuracy. ± 10C is fine.

In the middle run it would be nice to have something better
(thermal model for the battery might want environmental
temperature). If I measure a NTC which happens to be at -10 degC
from the mean then other XOs will show a deviation of 20 degC.

> > The thermistor was an after thought just in case we thought we could do
> > something clever with that info.  2 resistors and an unused A/D channel
> > is practically free.  It has zero influence on the thermal protection
> > circuits.

Ack. (I never meant that)

Greetings,

Frieder