Learn more about how the red thermometer works
The body temperature gun is composed of optical system, photoelectric detector, signal amplifier, signal processing, display output and other parts. The optical system gathers the target infrared radiation energy within its field of view, and the size of the field of view is determined by the optical components of the thermometer gun and its position. The infrared energy is focused on the photodetector and converted into a corresponding electrical signal. The signal passes through the amplifier and signal processing circuit, and is converted into the temperature value of the measured target after correction according to the internal treatment algorithm of the instrument and the target emissivity.
In nature, all objects with a temperature higher than absolute zero are constantly emitting infrared radiation energy into the surrounding space. The amount of infrared radiation energy of an object and its distribution by wavelength are closely related to its surface temperature. Therefore, by measuring the infrared energy radiated by the object itself, its surface temperature can be accurately measured. This is the objective basis on which infrared radiation temperature measurement is based.
A black body is an ideal radiator that absorbs radiant energy of all wavelengths without energy reflection or transmission, and its surface emissivity is 1. However, almost all actual objects existing in nature are not black bodies. In order to clarify and obtain the distribution rules of infrared radiation, an appropriate model must be selected in theoretical research. This is the quantized oscillator model of body cavity radiation proposed by Planck. Planck's law of black body radiation was derived, that is, the black body spectral radiance expressed in wavelength. This is the starting point of all infrared radiation theories, so it is called the black body radiation law. The radiation amount of all actual objects depends not only on the radiation wavelength and the temperature of the object, but also on factors such as the type of material, preparation method, thermal process, surface state and environmental conditions of the object. Therefore, in order to make the black body radiation law applicable to all real objects, a proportional coefficient related to the material properties and surface state must be introduced, that is, the emissivity. This coefficient represents how close the thermal radiation of an actual object is to blackbody radiation and has a value 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 known. The main factors that affect emissivity are: material type, surface roughness, physical and chemical structure, and material thickness.
When using an infrared radiation thermometer gun to measure the temperature of a target, you must first measure the amount of infrared radiation of the target within its wavelength range, and then use the thermometer gun to calculate the temperature of the measured target. The temperature gun is proportional to the amount of radiation in the band; the temperature gun is proportional to the ratio of the radiation amount in the two bands.
