Principle of Infrared Radiation Thermometer

Radiation thermometers are non-contact temperature measuring instruments, whose design is based on the correspondence between the thermal radiation properties of an object and its temperature. It is characterized by a wide temperature range and a complex principle structure; when measuring, the temperature-sensing element does not come into direct contact with the object under test and does not destroy the temperature field of the item under test. It is commonly used to determine the temperature or surface temperature of moving, rotating, or rapidly reacting high-temperature objects above 1000°C. Still, it does not directly measure the actual temperature of the item being measured. The measured temperature is affected by factors such as the emissivity of the object, the intermediate medium, and the measurement distance.

1. Infrared thermal radiation thermometry principle

In nature, all objects whose temperature is higher than absolute zero (-273.15℃), due to the thermal movement of molecules, are constantly radiating electromagnetic waves, including infrared waves, to the surrounding space, and the relationship between the energy density of the radiation and the temperature of the object itself is in accordance with the law of radiation.

An infrared radiation thermometer works on the principle of the quadratic law by detecting the infrared energy emitted by an object and infers the radiated temperature of the object. In an infrared thermal radiation temperature sensor, a thermopile as a measuring element converts infrared energy into thermoelectricity, which is then output as a detection signal after signal processing.

2. Infrared thermal radiation pyrometer structure

The infrared thermometer consists of an optical system, photodetector, signal amplifier and signal processing, display output, and other parts. The optical system converges the infrared energy of the target in its field of view, focuses it on the photodetector, and converts it into an electrical signal, which is converted into a temperature value of the target to be measured.

3. Radiation thermometers in industrial applications

Radiation thermometer is widely used in modern industrial production, especially in metallurgy, foundry, medical, food, and other industries, but because its application of the temperature measurement principle is more complex, the number of people who can skillfully use it is relatively small, which requires enterprise staff to further understand the principle of radiation thermometer and the way it works, to play its maximum effective use-value. The first step is to select the appropriate type of radiation thermometer according to the actual requirements of the production. Each radiation thermometer is used in a different range, and there is an optimal temperature range for each. When used in temperature environments outside of this range, it can have a more or less precise impact on the accuracy of the temperature measurement, affecting industrial productivity and product quality. For example, the temperature environment of an infrared thermometer used in the medical field is vastly different from the temperature environment of the metallurgical industry, and the two use completely different types of radiation thermometers, which can cause serious data distortion if misused. Therefore, the user must identify the specific scope of use of the radiation thermometer and choose the correct type of radiation thermometer. Secondly, attention should also be paid to the distance between the radiation thermometer and the object to be measured. Choosing the optimal distance for temperature measurement will be more conducive to obtaining accurate temperature data. The distance is determined by taking into account the size of the object to be measured and the personal safety of the person taking the temperature measurement. Finally, attention should also be paid to the influential role of the temperature measurement environment. If the temperature measurement site is dusty and other influencing factors are large, the environment needs to be cleaned in advance to create a temperature measurement environment free of objective interference and obstruction.