The Tech Behind Thermocouples

Thermocouples can be used to measure certain temperatures and measure their change over time. They’re typically used in research, industrial processes, and scientific laboratories.

So, what exactly are they, and how do they work?

In this post, we’ll cover thermocouple basics, explain how they’re used, and explain the colour codes & why they’re so important in the field of science.

The Technology Behind Thermocouples: How They Work and What to Know

The Basics of Thermocouples

The basics of thermocouples rely on three effects which are;

Thomson effect

This effect dictates that when an electric current flows along a conductor with a temperature gradient, the voltage is absorbed or emitted depending on the current and heat flow direction.

Thompson is a word you can use to describe the variation in rate and direction of temperature at a precise position.

See beck effect

This effect dictates that when two conductors forming a junction are subjected to a difference in temperature at the connecting point, it shows magnetic properties. This phenomenon occurs due to electrons migrating from the hotter end of the conductor to the colder end, which can be termed thermos-magnetism.

Peltier effect

Peltier effect states that heat is either liberated or absorbed at the intersection when an electric current flows past a thermocouple junction. The rate of heat absorbed or liberated is directly equal to the electric current flowing in the conductor.

Assembling of a Thermocouple

A thermocouple consists of two different metal wires (like iron or constantan) connected at a junction. The junction is categorized into three types depending on its purpose and characteristics. It is discussed below.

Exposed junction

When you want a quick response, you use an exposed junction. As the name suggests, this junction type is exposed outside of the protective cover.

The type of conductors you may use to make the sensor depends on the calculating range of the temperature. It is mainly used to detect gas temperature.

Grounded junction

This type of junction is formed by two thermocouple conductors welded together with a protection cover. This form of the junction is more potent and provides a fast response. It is used to measure the temperature in the acidic area.

Ungrounded or insulated junction

This junction is similar to the grounded junction, but the conductors are entirely separated from the protective cover; instead, an insulator surrounds it. It gives a slower response to temperature since heat must travel through both the protective cover and the insulator. This junction is applicable primarily in high-pressure works.

How a Thermocouple Works

The primary function of the thermocouple is to measure the temperature. It consists of two different conductors connected on both ends, called junctions.

When you heat or cool one of the junctions, you create a difference in temperatures on both junctions. One junction will be cold and the other hot.

Temperature variations on both junctions lead to the migration of electrons from the hot end to the cold end, generating an electromagnetic force in the circuit. If the temperature is the same on both junctions’ ends, then emf is the same, which means there is no current flow through the thermocouple circuit.

Application of Thermocouples

The thermocouple is widely used in the field of science. Some of its applications may include:

• They are the temperature sensors in the thermostats and flame sensors in safety devices at homes or offices
• They are used in industries to continuously evaluate the temperature of kilns, gas turbine exhaust, diesel engines, and more
• In food and beverages, they provide consistent temperature to ensure precise cooking
• They are also used to detect the temperature in chemical plants

A thermocouple is an effective tool in these fields due to its accuracy in measuring temperature.

The Tech Behind Thermocouples: Final Thoughts

Thermocouples are relatively adjustable, rough, and simple devices that can be made into small measurements. They can operate over a large spectrum of temperatures. Also, they are cheap and can be replaced easily.

However, to ensure they work well and can measure the desired and precise quantity, they need to be understood. This article has explained everything you need to understand thermocouples.