Identification

• Thermocouple wire sheathing is color coded to identify the type. The most commonly used types are Type J, K or T. The common or negative lead is red. The Type J positive lead sheathing is black, the Type K positive is yellow and the Type T positive is blue.
  
  

Accuracy

• Thermocouple wire accuracy depends on the application and manufacturer's specifications. The two accuracy categories are standard and special limits of error (SLE). Standard accuracy wire generally has twice the error limits of SLE wire.
  
  

Grade

• Thermocouple wire can be used to make a junction if it is rated as the same grade. Extension grade wire should only be used to connect a thermocouple to an instrument.
  
  

Recommended Length

• The maximum length of thermocouple extension wire required to reach an instrument should not exceed 100 feet with 20 American wire gauge (AWG) or larger wire. Environmental factors such as electromagnetic noise can affect the measurement accuracy.