Do I need thermocouple extension or compensating cable?
Thermocouple extension cables are made from the same conductor material as the thermocouple and are designated with the letter 'X' after the thermocouple type, so KX, TX, JX etc.
Thermocouple compensating cables are made from lower cost conductor materials which have the same thermoelectric properties as the thermocouple, provided that the interconnection point to the thermocouple material is below a certain temperature – as shown below. Compensating cables are designated by the letter 'C', so KC, NC, RC, SC etc.
Compensating cables ar available for Type K, N, R and S thermocouples with the cost saving advantage most noticeable for Types N, R and S unless a Type K thermocouple has a very long run of cable. For Types R and S however, extension cables are not available, so compensating cables for these types is the standard method for connecting them to instrumentation.
There is usually a 3rd letter added to the compensating cable (A or B), so KCB, RCA etc. which designates slightly different characteristics as explained below.
Thermocouple Extension and Compensating Cables