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Originally Posted by leejsmith
there is a xls spread sheet for calculating the curve of the thermistors. Will the mv reading work in place of the joystick port readings ?
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Absolutely.
You just need to calculate the resistance of the thermistor at the three given temperatures from your readings. Knowing the +5v, the voltage at the thermistor (your DAQ reading) and the resistance of the series resistor, you can figure this out. (5V-Vtherm)/(Vtherm/R)=Rtherm I think. Plug in the Resistance and calibration temperature for the three temperatures and you're good to go.
Good excel sheet. I did all my calculations myself but I just checked it against that sheet and it give the exact same answers for the SH-H coefficients using a slightly different method.
The ISEE software control language lets you put these equations into it so you can get a calibrated temperature output directly. It's a bit buggy but works, just don't feed it divide by zero problems or it will crash.
A sample might look something like this:
@RES1=(5 + (@CH1/1000)*-1)/((@CH1/1000)/40000) =====> (the thermistor resistance.)
@LOG1=LOG(@RES1) =====> (natural log of the resistance)
@TEMP1=0.00147408 + 0.00023704*@LOG1 + 0.00000010839*@LOG1^3 =====> (A,B and C coefficients, the steinhart-hart equation )
Tags: @CH1 is ADC input, @RES1, @LOG1, @TEMP1 are analog variables
There are nicer ways but this works.