A thermocouple is an instrument to measure temperature. It consists of two substances which are distinctly different. One wire made of each element is taken. Then these two wires are fused together at one end. On the other end, there is a thermometer or some other device which is compatible with a thermocouple. You can utilize thermocouples to read almost any temperature since it supports a wide range of thermal measurements.
1. Why Do We Need to Know How Thermocouples Work?
The thermocouple temperature sensor is an extremely common equipment. You can find it being used for personal purposes in households and for professional uses in industries as well. This high level of versatility is the reason behind its popularity. It is also the reason why you need to know how it functions. Because this knowledge will help you to utilize this instrument in times of need.
So let us enlighten you about the intricacies inside a thermocouple. We will know about the structure, categories and supported ranges of temperature of thermocouples.
2. Different Thermocouple Types
As we mentioned before, a thermocouple is mainly built on the amalgamation of two different metals. So much of the categorization of thermocouple temperature sensor depends on this combination.
The two metals fusing with each other also fuses their characteristics in the process. This dictates the resulting range of supported temperatures, the durability of the instrument, its application compatibility, vibration resistance and chemical resistance.
Base Metal Thermocouples
As the name implies, these thermocouples are made of base metals. The base metal thermocouples have subcategories such as type E, J, K and T. These are much more common and more affordable than the other class of thermocouples. That is because, common inexpensive metals like copper, iron and nickel are used in their structure. There is usually a protective sheath on these thermocouples based on the application it was built for. You can use them to measure low to medium temperatures.
Noble Metal Thermocouples
These cost a little more than base metal thermocouples. Their subcategories include type B. R and S. The reason behind their high price is their platinum conductors which can provide much greater resistance. Because of their stable service and long durability, these are used in industrial scales to measure high temperatures.
3. Thermocouple Construction
The main theme of thermocouple temperature sensor is connecting two distinct metals through one end. For these, one needs to wield the two conductors together at one measuring point. They help each other to get insulated along the length.
A protection sheath is applied to thermocouples for working at a medium or high range of temperatures. The medium range usually measures from 400-degree to 1200-degree Celsius. The sheath typically consists of stainless steel or alloy 600. A ceramic sheath is used for high range temperatures which measure above 1100-degree Celsius.
4. Mineral Insulated Thermocouples
There are certain thermocouples which are insulated by minerals. The conductors inside are protected by a metal sheath on the outer side. They are kept apart via a filling of highly compacted magnesium oxide powder. They are not allowed to meet any point except the fixed junction. For ensuring maximum protection of the conductors, the whole construction is hermetically sealed.