I got a NI USB 9213. The CJC reading is around 0.7 V. How it tranform to degree C or degree F? I know there is a formula degree C = voltage V *100, but it doesn't make sense here. Where is the problem? Thanks a lot

Hi allofdogs, This page from the cRIO manual explains the conversion, albeit for cRIO: Converting NI 9213 Data (FPGA Interface). However, DAQmx returns USB-9213 _cjtemp data in the +/-2.5 V range, so don't multiply by 32. Note that the isothermal offset constant may be different for different types of chassis (explained in Isothermal Errors and Cold-Junction Compensation (CJC) Data Scaling for the NI 9211E and NI 9219E). The equation in the cRIO manual subtracts 1 degree C to account for isothermal offset, but on the USB-9213 you should subtract 0.45 degrees C. This should leave you with: Calculate the resistance of the thermistor: RT = (10000 × CJC Data) ÷ (2.5 – CJC Data) Calculate the CJC temperature: T = [ 1 ÷ [A + B(ln(RT)) + C(ln(RT))3]] – 273.15 – 0.45 where T = temperature in °C A = 1.2873851 × 10-3 B = 2.3575235 × 10-4 C = 9.4978060 × 10-8 Brad

Multifunction DAQ

NI 9213 Thermocouple CJC voltage reading

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Ok, thanks for your reply and help !!!

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Multifunction DAQ

NI 9213 Thermocouple CJC voltage reading

Re: NI 9213 Thermocouple CJC voltage reading