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Topic: Innacuracy in converting thermistor resistance to temperature. (Read 2 times) previous topic - next topic

Krupski


Quote
If I use an LM-34 (10 mV/degree F) then my range is from close to 0 deg.F to 110 deg. C (also quite a useful range).


That's a neat trick.  ;)

Lefty



Oops... what a big difference one letter makes. I corrected my typo!  :)
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retrolefty

Quote
If I use an LM-34 (10 mV/degree F) then my range is from close to 0 deg.F to 110 deg. C (also quite a useful range).


That's a neat trick.  ;)

Lefty

Krupski


Depending on what accuracy you are looking for, a 1-point calibration in the middle of the temperature range (as I suggested) may be good enough, in which case you have to use the B-value from the datasheet in your calculation. If that isn't accurate enough, use a 2-point or even 3-point calibration, or a different sort of temperature sensor.


That's the best option. Something other than a thermistor.
Gentlemen may prefer Blondes, but Real Men prefer Redheads!

Krupski

#11
Dec 12, 2012, 09:56 pm Last Edit: Dec 12, 2012, 10:00 pm by Krupski Reason: 1


Or better yet... use an LM-35.....  :)


Or LM34, which has more than double the sensitivity of the LM35 and can read temperatures below 2C without a negative supply. Or DS18B20.


All depends on the application. For example, if I use an LM-35 (10 mV/degree C) and an Arduino with the A/D reference set to 1.1 volt internal, I can get a range of temperature readings from close to 0 deg.C to 110 deg.C (quite a useful range).

If I use an LM-34 (10 mV/degree F) then my range is from close to 0 deg.F to 110 deg. F (also quite a useful range). (fixed typo)

I just tossed out "LM-35" because that's what I'm used to using. In other cases, the LM-34 would be a better choice.

Really, the point of my comment was "don't use a crappy non-linear thermistor, use a nice linear solid state device"!  :)
Gentlemen may prefer Blondes, but Real Men prefer Redheads!

dc42

Depending on what accuracy you are looking for, a 1-point calibration in the middle of the temperature range (as I suggested) may be good enough, in which case you have to use the B-value from the datasheet in your calculation. If that isn't accurate enough, use a 2-point or even 3-point calibration, or a different sort of temperature sensor.
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