Data Acquisition (DAQ) and Control from Microstar Laboratories

Knowledge Base: Hardware

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Q10024 Thermocouple vs. hookup wire at panels

Tags: Help, DAP, thermocouple, termination, cold junction

Applies to: All DAP models, termination boards

I need to run connections from thermocouple connectors on my panel to the inputs on a MSTB009 termination board. Should I use thermocouple wire or regular hookup wire for this?

For most systems, it doesn't make a lot of difference. The answer depends on how you measure the ambient temperature for the cold junction compensation. You want to measure the CJC temperature at a location that closely matches the temperature at the ends of your thermocouple lead wires. Wherever that is.

For best accuracy, the reference temperature should be measured close to the thermocouple connectors, with a panel-mounted sensor. For this case, you should terminate your thermocouple wires at the panel connector, and route your signals from there through a pair of well matched copper hookup wires to the termination board. There will be no additional thermocouple effects or temperature-induced offsets between the panel and termination board.

If your system is not subject to thermal gradients of any significance, the CJC sensor mounted on the termination board gives a very close approximation to the temperatures everywhere on the termination board. When you use this sensor, it is a little better to continue with thermocouple hookup wire all the way to the termination board terminals. Be sure you do not get the thermocouple hookup wire leads reversed, as this will introduce some small stray reverse-thermocouple effects that might slightly degrade your measurement accuracy.