Thermocouples come in many different forms, all with their own unique characteristics and features, but all are used as sensors to measure the temperature within industrial and scientific settings. You can find thermocouples across the whole spectrum of the industrial market from Oil and Gas to Pharmaceutical to BioTech, these industries choose to use thermocouples because of their low cost, wide temperature range and high-temperature capacity, along with their durable and resilient nature. In the rest of this guide, we’ll take a look at the seven major types of thermocouples, what makes them unique and the applications you can use them for. Check out our full range of temperature sensors and thermocouples here!

The Design of a Thermocouple

But before we get into the sevendifferent types of thermocouples that may be of use to your business, it’s worth outlining the design of the typical thermocouple and how this allows them to perform to the highest quality. Most thermocouples are designed with two wire legs made from different forms of metal, these two wires are then welded together at one end creating a thermocouple junction. It is at this junction between the two metals that the temperature is measured, as a change in temperature at this point leads to a voltage being created. This voltage can then be interpreted utilising thermocouple reference tables to allow for the temperature to be calculated.

The Seven Most Common Forms of Thermocouples

Each form of thermocouple has its own unique characteristics from temperature range and vibration or chemical resistance to durability and application compatibility. The four most common types of thermocouples, Type J, K, T and E are all made from base metals, while Type R, S and B thermocouples are made using Noble Metals, making them suitable for higher temperature applications.

  • Type K Thermocouples –The Type K thermocouple is one of the most commonly used across the industrial market, providing a low cost yet highly accurate and reliable solution with a wide temperature range, from -270 to 1,260 degrees Celsius. Type K thermocouples are manufactured using a Nickel-Chromium or Nickel-Alumel combination and is widely found within nuclear applications due to their relative radiation resistance.
  • Type J Thermocouples – Another common and widely used thermocouple is the Type J which is an Iron-Constantan pairing, it’scosting, and reliability are similar to the Type K, however it has both a smaller temperature range and much shorter lifespan when working within high temperatureenvironments but is well suited for highly oxidative atmospheres.
  • Type T Thermocouples – This form of thermocouple is manufactured using Copper and Constantan, making it very efficient at working at extremely low temperatures such as anywhere between -270 to 370 degrees Celsius. With it’s ability to work in low temperatures environments, Type T thermocouples can be found in a range of cryogenic applications.
  • Type E Thermocouples – The Type E thermocouple provides a stronger and more accurate signal than both Type K and J thermocouples due to it’s more stable base metal coupling of Nickel and Chromium.

Nobel Metal Thermocouples

  • Type S Thermocouples – Often manufactured with a ceramic protection tube, rather than the typical protective sheath used to protect other thermocouples from the external atmosphere. The coupling is manufactured using a Platinum, and 10% Rhodium pairing making it extremely useful in high temperature applications, with a maximum temperature range of 1,600 degrees Celsius. Most commonly Type S thermocouples are found within BioTech and Pharmaceutical environments.
  • Type R Thermocouples – Again manufactured with a Platinum and Rhodium pairing, though at a higher percentage of Rhodium with 13%, they are again an effective sensor for high temperatureenvironments, providing a higher output and improved stability allowing a more reliable and accurate reading. But due to the higher percentage of Rhodium, Type R thermocouples also come at a much higher cost.
  • Type B Thermocouples – This form of thermocouple has the highest temperature limit of all the other forms of thermocouples mentioned above, making it perfect for use within high temperature environments, and due to its 30% Rhodium makeup it provides highly accurate reading and stability at temperatures as high of 1,700 degrees Celsius.

So, there you have an overview of the seven most common forms of thermocouples used within the industrial market to measure temperature changes within extreme temperature environments. If you’d like to discuss your business’ exact requirements, then why not give our expert team a call today on 0845 688 7332 or why not browse our full range of temperature sensors and thermocouples now!