1. Principle of Infrared Thermography

In nature, when the temperature of an object is higher than absolute zero (-273℃), infrared radiation is constantly generated. Infrared thermal imager is an instrument that detects the intensity of infrared radiation on the surface of an object and presents the shape and outline and distribution of the surface of the object, so as to facilitate human eye observation. The brightness and shade of the infrared images reflect the surface temperature of the object. By detecting the surface temperature and temperature field of the object, we can determine whether the equipment has defects.

2. Factors affecting the Measurement Accuracy of Infrared Thermal Camera

1) The Emissivity of the Measured Object

Emissivity is a physical quantity that describes the radiant energy of the measured object relative to the blackbody. The radiation energy obtained from the measured object by the infrared thermal imager is directly proportional to the emissivity of the measured object. In the measurement process, if the emissivity of the measured object is not paid attention to and the emissivity of the infrared thermal imager is improperly set, there will be an error between the measured temperature and the actual temperature of the object. The emissivity is also related to the measurement angle, the larger the measurement angle, the greater the error.

2) Spatial Resolution of Infrared Thermal Camera

The spatial resolution of the infrared thermal imager refers to the angle of view projected into space by a single sensor after being transformed by the optical system, expressed in milliradian (MRAD). Each sensor of the infrared thermal imager can be regarded as one infrared thermal imager, so the spatial resolution of the infrared thermal imager is equivalent to the distance coefficient of the infrared thermal imager. In practical application, the distance coefficient of the thermometer is often ignored, resulting in a large measurement error. When infrared thermal camera is used to measure small targets remotely, the infrared thermography with large distance coefficient should be selected to ensure the accuracy of temperature measurement.

3) Setting the Temperature Measuring Range of Infrared Thermal Camera

Infrared thermal imager is a very important performance index when measuring temperature range. Each type of infrared thermal imager has its own specific temperature measuring range. Generally speaking, the narrower the temperature measurement range, the higher the resolution of the output signal of monitoring temperature, the higher the accuracy and the more accurate the temperature measurement. If the temperature range is too wide, the accuracy will be reduced and the error will be large. Therefore, the user in the choice of infrared thermal imaging instrument must be considered accurate, comprehensive, neither too narrow, not too wide.

4) The Influence of Environment on Infrared Temperature Measurement

Due to atmospheric absorption (water vapor, carbon dioxide, etc.), infrared radiation will have a certain amount of energy in the process of transmission attenuation, but most of the infrared thermal imager is no for this compensation method, as a result, while the outdoor for infrared temperature measurement, in order to reduce the error, should choose in no rain, no fog, air relative humidity is not more than 75% of the environmental conditions.

3. Summary

Yoseen infrared thermal imager is widely used in electric power, railway, chemical industry, security and other fields, but its reliability and accuracy are affected by many factors, in the actual use, we should fully consider various factors that may affect the accuracy of measurement, take correct and effective methods to obtain real data.