How do thermocouples work? quick tour

Thermocouples are durable temperature sensors found in many industrial applications. Learn what thermocouples are, how they work, and why they are so popular.
Thermocouples are electrical devices used to measure temperature. Their accuracy, fast reaction time and ability to withstand severe vibration, high pressure and extreme temperature make them ideal for wide application. But how do thermocouples work?

Working principle of thermocouple

The working principle of the thermocouple follows the Seebeck effect, that is, the thermoelectric effect, which refers to the process of converting thermal energy into electrical energy. This effect describes the voltage generated when two different conductors are connected and how the voltage generated varies with temperature.
The basic design of the thermocouple involves two different metal wires, each of which has different electrical characteristics at different temperatures. Two metals contact at one end - contact, twist or weld; This is the measuring point. The other end is the connection point, so called because it is connected to the voltage reader. When the temperature of the measuring point changes, the electron density of each metal wire will also change. The electron density of this change is the voltage, which is measured at the connection point.
Note that thermocouples do not actually measure absolute temperatures. Instead, they measure the temperature difference between the measurement point and the connection point. This is why the thermocouple also needs cold junction compensation to ensure that the ambient temperature at the cold junction terminal will not change the measurement results, so as to obtain more accurate readings.

Metal pairing in thermocouples

To make the thermocouple work normally, its two wires should provide as much contrast as possible in all electronegativity aspects. In this way, the voltage reader can detect the maximum thermoelectric voltage difference.
Base metal thermocouples (called J, T, K, E, and N types) produce higher thermoelectric voltages than more expensive precious metals (called R, S, and B types). However, the latter type can withstand temperatures up to 3092 ° C (1700 ° C) or higher. Some common metal pairs are iron and copper nickel (type J), copper and copper nickel (type T), and nickel chromium and nickel aluminum (type K). Precious metal thermocouples are usually made of platinum and rhodium (types S, R and B).
Weilian produces a wide range of high-quality thermocouples with various temperature ranges, configurations and materials. For more information on how thermocouples work, please contact our temperature measurement experts. Tel./WeChat 18717811268 Huang Gong