Various industries and fields use thermocouples to gauge temperatures during their work operation. A thermocouple is made of two dissimilar types of metal wires connected at the thermal junction- the type of thermocouple created depends on the combination of metal wires used.
Various types of thermocouples with different wire combinations are available in the market. However, to select the right thermocouple suitable for your work project, you need to know the temperature expectations and the environment in which the thermocouple will be placed. Read on to gain a proper understanding of the different types of thermocouples:
Type B
With a temperature range between 2500- 3100 degrees, the type B thermocouple is commonly used in inert and oxidizing atmospheres. The Type B thermocouple has an alloy combination of Platinum{ 30% rhodium) crimped with a Platinum (6% rhodium) wire. Though similar to type S and type R, the type B thermocouple has a lower output and is susceptible to calibration drift and grain growth.
Type S
The Type S thermocouple has an alloy composition of Platinum/Platinum(10% Rhodium). The type S thermocouples are employed for high-temperature applications; however, they must be protected with ceramic insulators and non-metallic protection tubes. This is because continuously using the type S thermocouples for high-temperature operations causes excessive grain growth, leading to degradation and mechanical failure. There’s also a likelihood of rhodium diffusing into the pure platinum conductor, causing negative calibration drift and reduction in output.
Type K
Also known as Chromel-Alumel, Type K is the most common type of thermocouple in industrial use because of its reliability, affordability, accuracy, and wide temperature range. The type k thermocouple is best suited for continuous neutral or oxidizing atmospheres and is most adapted to continuous temperatures between 538C to 1100C.
The type K thermocouple sensor styles include Insulated mineral thermocouple, type K swaged, Tip thermocouple, miniature thermocouple, heavy duty thermocouple, general purpose, and ATEX/IECEx Approved Type K thermocouples.
Type J
The type J thermocouple has a temperature range of 0C to 760C and can be safely used in reducing, inert, or vacuum atmospheres. It can also be applied in oxidizing atmospheres below 550C. Likewise, the type K thermocouple has a minimum and maximum continuous operating temperature of -210C and 800C, respectively. It has various thermocouple styles which can be used for multiple applications.
Type N
The type N thermocouple is a newly introduced thermocouple type made to replace the type k thermocouple and have better functions. It has a temperature range between 0C to 1260C and has an alloy composition of Nicrosil and Nisil. Unlike the Type K thermometer, the Type N was built to have a higher resistance to oxidation-related drifts and handle higher temperatures. Likewise, it has much greater stability against nuclear bombardment.
Type T
The type T thermocouple has an alloy combination of copper and nickel and is often referred to as copper-constantan. This thermocouple type is suitable in an inert, reducing, and oxidizing atmosphere with a temperature range between -250C and 400C. However, at temperatures exceeding 400C, its copper element becomes susceptible to oxidation.
Industrial Temperature Measurement
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