Wondering what a thermocouple is? A thermocouple is a temperature sensor that generates a voltage signal based on the temperature difference between two different metals or alloys. It consists of two dissimilar metal wires joined together at one end, forming a junction. When this junction is exposed to a temperature gradient, it produces a small voltage (which is known as the measuring junction) that is proportional to the temperature difference. You can read more about these sensors in our bespoke Thermocouples selection guide.
This phenomenon is known as the Seebeck effect. It occurs because different metals have different electron configurations, resulting in varying electron densities and thermal conductivities. As a result, when the junction is exposed to a temperature difference, an electric current is induced due to the flow of electrons from the hotter metal to the colder metal.
The voltage produced by the thermocouple can be read and measured by a voltmeter or a specialized temperature measurement device. By knowing the relationship between the temperature and the voltage output, typically described in a calibration table or equation specific to the type of thermocouple being used, the temperature at the measurement point can be determined.
Types of thermocouples
There are a wide range of thermocouple types available, each with different characteristics such as temperature range and their robustness. Each thermocouple is defined by a letter such as K-Type. Common thermocouple types also include: Type J, Type K, Type L and Type T
The letters refer to the type of materials used which indicates what temperature they are usable at. For example, J-Type is iron and copper-nickel and is useable from around 0°C to 816°C, depending on other characteristics. Some thermocouples come with an additional sheath that insulate the wires to prolong their life.
Thermocouples are widely used in various industries for temperature monitoring and control applications. They are ideal tools for the measurement of high temperatures and are a popular choice as they are so robust, reliable and an affordable solution.
What are Thermocouples used for?
They can be used in many applications, both domestic and industrial. Some examples include:
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