Best Practice: How to Properly Terminate Thermocouple Wires

First let's discuss Thermocouples!  A thermocouple is a temperature sensor device used to measure temperature in various industrial, scientific, and commercial applications. It consists of two different metal wires or alloys joined together at one end, called the sensing or measuring junction, and connected to a temperature-measuring instrument at the other end.  When the two different types of metals are joined together, they produce a micro-voltage proportional to the temperature. 

What happens in between that junction and the rest of the system is very important since, if the metals are changed - for instance - from thermocouple material to copper or tin - THAT forms another thermocouple junction and can add to, or subtract from the micro-voltage signal generated by the sensing junction in the process being measured.

If you are terminating thermocouple wire in any place other than the controller itself, consider using thermocouple terminal blocks.  They are made with the same materials as the original thermocouple and therefore if continued with thermocouple wire on the downstream side of the block, will not attenuate the original signal.

American Electrical, Inc. (AEI) sells Types J and K Thermocouple Terminal blocks - please see link below or call us at 804.379.2899 today!

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In the Industrial Controls Industry, the most popular Thermocouples are: Type K (chromel/alumel) and Type J (iron/constantan).  Type J has a more restricted range −40 °C to +750 °C than type K but higher sensitivity of about 50 μV/°C.  Type K is the most common general-purpose thermocouple with a sensitivity of approximately 41 μV/°C.   It is inexpensive, and a wide variety of probes are available in its −200 °C to +1350 °C range