Factors Affecting Indication of Infrared Thermometer
1 Principle of infrared thermometer
Any object is constantly radiating infrared energy. Infrared thermometers measure the temperature based on the infrared energy radiated by objects. The infrared thermometer is composed of an optical system, a detector, a signal processing device and a display screen. The infrared energy radiated by the object enters the detector from the optical system, and then is processed by the signal processing device, and finally displays the temperature of the measured object on the display screen. . Infrared thermometer belongs to non-contact measurement. Compared with contact measurement, it has the characteristics of fast, convenient, flexible and safe, and can measure some areas that are not easy to reach for contact thermometers. However, limited by some factors, the temperature measurement accuracy and accuracy of infrared thermometers are difficult to compare with those of contact thermometers such as thermocouples and platinum resistance thermometers.
Definition of radiation temperature: When the total radiation energy of an actual object is equal to that of an absolute black body, the temperature of an absolute black body is defined as the radiation temperature of an actual object.
2 Influencing factors
2.1 Setting of emissivity
Since the emissivity of an object is always less than 1, it can be seen from the definition of radiation temperature T0 = εT that the radiation temperature of an object is always less than the real temperature. The more the emissivity deviates from 1, the more the radiation temperature deviates from the true temperature. Although the infrared thermometer measures the temperature through the infrared radiation of the object, what it measures is the real temperature of the object, which leads to the first major factor affecting the indication value of the infrared thermometer: the emissivity setting.
At the same temperature, the ratio of the radiation output of the actual object to the absolute black body is the emissivity of the actual object, and the definition formula is ε = M/M0. There are many factors that affect the emissivity of the object, mainly including temperature, wavelength, emission direction and material surface physical properties, etc. Different objects have different emissivity, and the emissivity of the same object may change when conditions change. The indication value of the infrared thermometer is obtained by calculation, and the emissivity value is an important parameter involved in the calculation. The infrared thermometer obtains an indication close to the real temperature of the object by adjusting its own emissivity to be consistent with the emissivity of the measured object. value. The following examples illustrate the influence of the emissivity setting on the displayed value.
