Thermocouples: What Are They And How Do They Work?
Thermocouples are constantly secretly working all around you. But what are thermocouples and how do they work?
Put in the very simplest way possible; a thermocouple is a sensor that is used to measure temperature. It produces a small unique voltage at a given temperature which can then be measured and interpreted by a thermocouple thermometer. They are used for a measurement and control purposes, widely used in science and the manufacturing industry.
Thermocouple thermometers can be found in kilns, gas turbine exhausts, diesel engines, ovens and industrial processes.
They work because of the thermoelectric effect, which is when a conductor generates a voltage when subjected to a thermal gradient. A combination of two different metals produces the voltage, but it can be a number of different metals and calibrations.
A thermocouple can be calibrated in a number of different ways, but there are four which are more common than others. These most common calibrations are referred to as calibration J, K, T and E. Each one has a different temperature range and environment that it is useful for. By making the wire in the thermocouple thicker, you can also increase the maximum temperature that it will measure.
When purchasing a thermocouple, as with most products, it is best to follow a set of guidelines to ensure you choose one to suit your needs. The first thing that you will want to do when selecting a thermocouple to use is to check the temperate range that it covers. You will also want to take into account the chemical resistance of the thermocouple or the sheath material as well as the abrasion and vibration resistance. You may also want to make sure that you are aware of what installation requirements the thermocouple has, as it may be required to be compatible with existing equipment for example.
The type of thermocouple is also key. The three main sub-categories are Grounded, Ungrounded and Exposed thermocouples.
A Grounded thermocouple has the wires physically attached to the inside of the probe wall which can help with the direct reading of temperatures. An Ungrounded thermocouple is detached from the probe wall, which can benefit from electrical isolation. An Exposed thermocouple protrudes out of the tip or the sheath and is therefore exposed to all of the surrounding environment.
How and where you are trying to measure temperature will affect which thermocouples are suitable for your needs. Various different thermocouples will offer better or more accurate readings but only in certain conditions. Therefore it may be required to sacrifice response time or speed of reading due to the requirements of the environment in which you are measuring in.
MITSCO is a family run business which offers a huge range of instrumentation and sensor products, including thermocouples. Their entire product range is supported by fully trained staff and engineers with years of experience, meaning they can provide the support and advice that you require.
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