What is a Thermocouple?

A thermocouple is a type of temperature sensor. They are well known for being highly versatile and they can measure temperature over a wide range. They use electric currents and different metal types to measure temperature.

Thermocouples are part of our product portfolio here at Variohm. 

How does a Thermocouple work?

A thermocouple is constructed of two different metals joined at both ends. To measure temperature, one end of the thermocouple is exposed to heat, when this happens there is a continuous current flowing through the circuit, the current only flows if one junction is a different temperature to the other junction. Being exposed to a higher temperature will make the current flow faster, the speed of the current can be measured and this can be converted into a temperature measurement. This will depend on the type of metals being used within the thermocouple. 

Different Types of Thermocouple

There are different types of thermocouple, they can be distinguished by the different metals they are using within them. Each different type will have different parameters as the speed of the current will relate to a different temperature depending on the metal being used. 

The most common Thermocouple types are; E,J,K,N and T, the comparison chart below gives more information on each type

Thermocouple Junctions 

Grounded Thermocouples are the most common type of thermocouples, both the thermocouple wires and the sheath are welded together to form one junction at the end or tip of the thermocouple. They have very good response times as the thermocouple itself makes direct contact with the sheath which enables the heat to transfer quickly and easily. However, the thermocouple is more susceptible to electrical interference in this format as the sheath can come into contact with the atmosphere which can cause interference.

Ungrounded Thermocouples have the wires welded together but they are insulated from the sheath making them more stable.

Exposed thermocouples have the wires welded together and then directly inserted into the application. This gives an extremely quick response time but it does leave the wires open to corrosion. This style is only recommended if the application requires exposed junctions.  

What is a Thermocouple used for?

Because thermocouple can measure such a wide temperature range they are used throughout many different industries, some of their uses include;

• Industrial applications
• Scientific applications
• OEM applications
• Power Generation
• Oil and Gas
• Pharmaceutical
• BioTech
• Paper and pulp
• Cement 
• Everyday appliances - cookers, furnaces, toasters etc. 

Why choose a Thermocouple for your Application

Thermocouples are often selected for their wide temperature range, quick response time and low costs. 

The main drawbacks of using a Thermocouple are that they are not as reliable as temperature sensing alternatives; for example, RTDs tend to be more accurate.

Thermocouples from Variohm

We have a range of thermocouples on our website, these can be found in our temperature section.

Most of our thermocouples are made to order so for more information on thermocouples please contact us.