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10k Thermistor with CR1000X


MattB Jul 21, 2020 11:18 PM

Hi all,

I have a 10k thermistor I would like to measure with a CR1000X.

The sensor is a Second Wind SWI 10k thermistor.

Can I simply use the "Therm109" instruction for this?

If not, advice on the best instruction and method would be greatly appreciated.

Thanks very much,

Matt


JDavis Jul 22, 2020 09:17 AM

You need a fixed value resistor to complete the half bridge circuit. Check the documentation for the sensor to see if it has one internally. If the sensor is just a 2 wire probe (plus shield wire), it does not have a fixed value resistor in it.

The recommended fixed value resistor is a 3WHB10K. You need to wire the sensor in a manner to get this circuit. On a 3WHB10K, you would connect the short wire to a Vx channel, and connect the two wires of the probe into H and ground of the module. The L on the module would not be connected.

https://help.campbellsci.com/crbasic/cr1000x/Content/Resources/Images/halfbridge.png

The instruction to use is BrHalf. You then have to calculate the resistance. The formula to get resistance is shown in the help for the instruction.

https://help.campbellsci.com/crbasic/cr1000x/#Instructions/brhalf.htm?Highlight=brhalf

To go from resistance of the termistor to temperature, you need the formula specific to that sensor. Look in the manual for coefficients to use in the Steinhart-Hart equation.


MattB Jul 22, 2020 04:25 PM

Hi JDavis,

Thank you very much for your prompt and detailed response - most appreciated.

Thanks,

Matt

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