Bad reading of thermocouple on SCXI-1102

Hi,
Some of the thermocouple plugged in the SCXI-1102 give bad reading(unusual value). There is maybe an issue with the use of grounded and non-grounded thermocouple? Is the system need to be calibrated?
Thanks.

Hello gperron,
When you say some thermocouples give bad values, does this mean that you have some that give the correct value?  If so, try switching the ones that give you a correct reading with the ones that are giving a bad reading.  If the bad readings follow the thermocouples, you can conclude that those thermocouples are bad.  Are you using the built-in cold junction compensation on the SCXI-1303 to make sure you are getting the most accurate readings?
In general, thermocouples are floating sources and you measure them differentially with a bias resistor connected between the negative terminal and ground.  Page 3-4 of the 1102 User Manual describes connecting signals to the 1102.  The 1303 Installation Guide describes how to replace bias resistors, if needed.   
Thanks,
Laura

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