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What is a Type K 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 K thermocouple, one wire is made of chromel and the other wire is made of alumel.

Characteristics of Type K 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 an extremely wide temperature range (up to 1,150 °C for type K). 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. An important advantage of the type K over the type J thermocouple is that its leads are resistant to oxidation.

The hot junction of a thermocouple is where the two wires are welded together

Mineral Insulated K-Type Thermocouples





Suggestions for Thermocouple Type K

Type K thermocouples are a good solution for temperatures above 500 °C when RTDs reach their physical limits. You should also consider the use of a thermocouple if you need extremely small diameters and quick response times. 

Please note that as with every thermocouple, the cold junction needs to be compensated. Additionally, you need compensated cables and connectors with a thermocouple.



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