Thermocouple extension wire resistance


Thread Starter


When i Checked nickel chrome nickel aluminum thermocouples extension wires resistance it seems both have different resistance. 1 wire has half the resistance of another wire. why is it so? The materials seems to be same and also no of strands in wire same. did any have idea about it?

Thanks in advance
If I understand you correctly, one wire is made of a nickel chrome alloy and the other wire is made of a nickel aluminum alloy, and it is normal for thermocouple wire and extension wire for the wires to be made of different alloys. Each wire has its own resistivity constant based on the materials (alloy) involved, hence different resistance for a given length of wire. There may also be termination resistances that can contribute (significantly, if you have a bad connection). Get the manufacturer to provide you with the resistivity constants for the wires.

See the following link:

William (Bill) L. Mostia, Jr. PE
ISA Fellow, SIS-TECH Fellow,
FS Eng. (TUV Rheinland)
SIS-TECH Solutions, LP

Any information is provided on Caveat Emptor basis.

Curt Wuollet

It's the physical properties of the two materials Nickel Chromium is actually used to wind resistors and heater coils because it has fairly high resistance. The other alloy simply has much lower resistance per unit area.