Temperature Measurements with SCXI-1102

[VP]

1. The accuracy of the sensor used for the cold-junction compensation (CJC) in the terminal block SCXI-1303 is given +/- 1 degC. Does this mean that the accuracy of my temperature measurements are limited to +/- 1 degC?

2. The temperatures in our test enviroment can vary from 10 degF to 103 degF. Can the CJC sensor work accurately under these conditions? If not, what is the solution?

3. Does the CJC sensor drifts over, say, 6 month to 1 year time periods?

[RIO-Todd]

1. Thermocouples themselves are not highly accurate in regards to measuring temperature. Most thermocouple accuracies are +/- 1 degC if not higher.

2. The purpose of the CJC sensor is to measure ambient temperature at the terminal block (usually) to account for the temperature that the metal contacts from your thermocouple are at within your terminal block. If you heat up the CJC sensor, then you need to make sure that the temperature of the screw terminal contacts (between the thermocouple wire and the screw terminals of the 1303) is the same. It is usually optimal to keep the SCXI chassis in ambient room temperature and have only the thermocouple within the high temperatures you are measuring. The CJC is rated up to 55 deg C which is equivalent to 131 degF.


3. I have read through the specifications of the CJC sensor and there is nothing regarding drift. It is recommended that you calibrate your hardware (SCXI Chassis/module and data acquisition device) every year.