What is a Type J Thermocouple?
A thermocouple puts out a voltage signal related to the temperature difference between to points. It has no dedicated sensing element but instead consists of two joint wires made from different metals. In case of the type J thermocouple, one wire is made of iron and the other wire is made of constantan.
Characteristics of Type J Thermocouples
Thermocouples are the simplest sensors in the world – what is easier than just putting two wires together? A thermocouple is physically very robust and can measure in a wide temperature range. It can also be built in miniature diameters as small as 0.25 mm. As opposed to RTD like Pt100 and Pt1000, wire length and wire diameter do not cause measurement errors with thermocouples.
Generally speaking, a thermocouple’s signal is much weaker than that of an RTD. This makes it more sensitive to electrical interference. Also, if you require a high resolution, it may not be the best choice. A specific delicacy of the J-type thermocouple is that its leads are prone to oxidation.