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thermister data acquisition using cDAQ-9172

I would like to read temperature measurements from a series of thermisters using a cDAQ-9172 board and I am unsure of which module I need to do this.  I currently have an NI 9211 module but this specifies it is for a thermocouple input.  Can I use this module or do I need a different one?

thanks

Mike
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Hi Mike,

 

Thank you for posting to the NI forums.  For thermistor measurements, you will need to provide some form of current excitation to the transducer.  The 9211 does not provide any form of current or voltage excitation.

 

Instead, I would recommend using the NI 9219, which has built-in current and voltage excitation.  You could also use any of the other analog input modules, but again, you will have to make sure that they either provide excitation, or you will have to provide it externally.

 

I hope this helps.  Please post back with any further questions.

 

 

Ed W.

Applications Engineer

National Instruments

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Hi Mike,

Ed's suggestion to use the NI 9219 is a good one, since the NI 9219 can measure resistance without any external signal conditioning. However, you should be aware that the maximum resistance the NI 9219 can measure is 10.5 KΩ. There is a graph showing the temperature-vs-resistance curve of a typical thermistor in http://zone.ni.com/devzone/cda/tut/p/id/2948. Judging from that graph, if you need to measure temperatures below 0°C you will still need external signal conditioning (such as a shunt resistor in parallel with the thermistor).

Note that you will need to use the resistance variant of the DAQmx Create Channel VI, and then do your own scaling from resistance to temperature, since thermistor mode is only supported on channels _cjtemp0:3, not ai0:3.

Brad
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Brad Keryan
NI R&D
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