A Complete Guide To Different Thermocouples And Their Applications

Thermocouples are important devices with varying applications in monitoring and regulating temperatures and chemical conditions in areas like steel making. However, their use in applications that require more complex and accurate temperature monitoring and corrections such as where a variance of about 0.1 degrees is needed is more limited. This however has not to mean that the effectiveness of the devices is in any way much reduced when it comes to traditional applications.

Thermocouples have letter based classifications and can be identified using particular color codes. The most common types are types J, K and T which are black, yellow and blue respectively. Type J thermocouples are made from iron and constantan, type K from Nickel and chromium or aluminum while T is made from copper and constantan.

While thermocouples can measure their own temperatures, it is worth noting that they can err especially if they have just been in use. Other factors that can lead to inaccurate temperature readings include when the insulation between the two wires losses its resistance due to thermal conditions or moisture. It is also important to remember that thermocouples are electrical conductors and all caution should be taken to avoid danger of electrocution.

It is also important to remember that it is impossible to use thermocouples to determine the temperature on a junction. This is because thermocouples are devices which measure temperature gradient and it is impossible to have that at a single point. In order to compensate for the thermal lag that develops when the distance between a thermocouple and the heater element is substantial, a heat controller can be used to ensure greater accuracy.

Depending on the application, thermocouples have very big differences in both appearance and material construction. As such, there are distinct devices for applications in different industries such as plastics, food and pharmaceuticals. As an example, thermocouples used in the plastic industry come without magnesium oxide and they also feature a bayonet cap for ease of installation. Those used in pharmaceuticals usually have an annealed metallic sheath for ease of bending.

The efficacy of thermocouples is dependent on the alloy combinations it is made from. The right device for a particular application will depend on the sensitivity required as well as temperature range conceivable in that particular application. In any case though, most applications fit in with either of the three popular models: type T, type J or type K thermocouple.