When to use J Type and K Type Thermocouples


Choosing the right temperature sensors for a job can be bewildering, especially where the superficially similar J type thermocouples and K type thermocouples come into play. However, it doesn’t need to be as confusing as all that – and you don’t need to learn through trial and error when to use J Type and K Type Thermocouples. Each one has its own strengths and weaknesses, making them suited to different tasks and applications, so by knowing these differences, you’ll be up to date on which to use in no time!

J Type Thermocouples are temperature sensors made from iron and nickel/copper alloy (constantan) which are able to accurately measure temperatures between 0°C and approximately 816°C. It is the less expensive of the two thermocouple temperature sensors and offers reliable temperature measurement throughout its temperature range. While lacking the very high-temperature range that can be offered by its K Type rivals, the J Type Is nonetheless a very effective temperature sensor throughout its not-inconsiderable range, making it an excellent, cost-effective thermocouple at these temperatures.

K Type Thermocouples are the most popular thermocouple temperature sensors on the market today. While more expensive than J Type Thermocouples, the K Type is the more versatile of the temperature sensors, able to withstand temperatures between 0°C and 1260°C. This higher temperature range makes it much more useful at extreme heats than the J-type, although its increased cost means that it doesn’t tend to beat the J Type Thermocouples out at lower temperature ranges.

In addition to an increased temperature tolerance range, the K Type Thermocouples have another advantage in resistance and capability – their different metallic makeup. Whereas a J Type thermocouple is made up of iron and constantan, K type thermocouples are composed of a nickel/chromium alloy (chromel) and a nickel/aluminium alloy (alumel) which gives them much better protection against oxidation and acidity than the iron limbs of the Type J.

K Type Thermocouples are therefore perfect for use in oxidative environments and environments with a corrosive atmosphere or when immersed in an oxidative or corrosive fluid. In fact, the K Type Thermocouples work most effectively in a clean oxidising atmosphere, where a J Type may be oxidised and damaged. The k type thermocouples are also more useful at very high temperatures – up to 1260°C – allowing you to accurately measure temperatures even at these heats.

However, their slightly increased cost compared to J Type Thermocouples helps to ensure that the Type J continues to see use throughout lower-temperature applications and in non-oxidising atmospheres, which perfectly suit its temperature-measurement ability. As temperature sensors, the K type thermocouples and J type thermocouples may be superficially similar, but they are suited to a wide range of applications. For more information on temperature sensors, including Type J Thermocouples and Type K Thermocouples, and for more information on their applications and uses, feel free to call the experts at Cartridge Heaters on 0845 688 7332. They will be more than happy to help you find the perfect temperature sensor for your needs!

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