Thermocouple Accuracy Table by Type and Temperature

Updated Nov 22, 2017

Issue Details

I am reading the temperature of a chamber using two thermocouples of the same type but the readings are different. I have calculated the accuracy of my measurement hardware but it does not compensate for the difference in readings. What may be causing this phenomenon?

Solution

In addition to considering the accuracy of the measurement hardware, you should consider the inherent accuracy of the thermocouple. The accuracy of a thermocouple is affected by its type and temperature. See the table below for the maximum permitted error (in degree Celsius) for various common thermocouples that comply with IEC 584-2 (1982). 
 

In addition to accuracy based on the type of thermocouple, thermocouples have a specified range of temperatures over which they can operate. This can become a problem when extreme high temperatures are being read. Their ranges are determined by numerous variables, including the following:
  1. Type (i.e. J, K, E, T, RX/SX, N, CX)
  2. Sheath material
  3. Sheath diameter
The following website is an example of a thermocouple wire reference guide produced by a specific manufacturer that gives temperature range. International Thermocouple Color Codes

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