How do you calibrate an infrared thermometer?

How to calibrate an infrared thermometer?

I. Calibration can be performed using a blackbody radiation source and a standard thermocouple of accuracy class 2 or higher, a photoelectric pyrometer, or an infrared thermometer with a higher accuracy class than the infrared thermometer being calibrated

II. All objects with a temperature above absolute zero continuously emit infrared radiation energy into the surrounding space. The magnitude of an object's infrared radiation energy and its distribution across wavelengths are closely related to its surface temperature.

Therefore, by measuring the infrared energy radiated by the object itself, its surface temperature can be accurately determined. This is the objective basis on which infrared radiation thermometry is based.

Further Information:

I. Blackbody Radiation Law:

A blackbody is an idealized radiator that absorbs all wavelengths of radiant energy, with no reflection or transmission of energy, and its surface emissivity is 1.

It should be noted that blackbodies do not exist in nature, but in order to understand and obtain the distribution law of infrared radiation, a suitable model is chosen in theoretical research. This is the quantized oscillator model of cavity radiation proposed by Planck, which led to Planck's blackbody radiation law, i.e., the spectral radiance of a blackbody expressed in terms of wavelength. This is the starting point of all infrared radiation theories, hence it is called the blackbody radiation law.

II. The Influence of Object Emissivity on Radiation Thermometry:

Almost all real objects existing in nature are not perfect blackbodies. The amount of radiation emitted by all real objects depends not only on the radiation wavelength and the object's temperature, but also on factors such as the type of material constituting the object, the manufacturing method, the thermal process, and the surface condition and environmental conditions.

Therefore, to make the blackbody radiation law applicable to all real objects, a proportionality coefficient related to the material properties and surface condition is introduced, namely emissivity.

This coefficient represents how closely the thermal radiation of a real object approximates that of a blackbody, and its value is between zero and a value less than 1. According to the radiation law, as long as the emissivity of the material is known, the infrared radiation characteristics of any object can be determined.