Research on self-calibration error comparison method of infrared thermometer
1 blackbody radiation and infrared temperature measurement principle
All temperatures higher than absolute zero of the object are constantly sending out infrared radiation energy to the surrounding space. The size of the object's infrared radiation energy and its distribution by wavelength and its surface temperature has a very close relationship, therefore, through the measurement of infrared energy radiated by the object itself, the thermometer's optical system in the detector into an electrical signal and through the infrared thermometer's display part of the surface temperature of the object to be measured, it will be able to accurately determine the temperature of the surface, which is the infrared radiation based on the temperature measurement Objective basis.
Infrared thermometer features: non-contact measurement, wide temperature range, fast response time, high sensitivity, but due to the impact of the emissivity of the object under test, it is almost impossible to measure the real temperature of the object under test, the measurement is the surface temperature.
The standardized calibration method of infrared thermometer is to use a blackbody furnace calibration. Blackbody is defined in any case on all wavelengths of incident radiation absorption rate is equal to 1 of the object, the blackbody is an idealized object model, so the introduction of a radiation coefficient with the nature of the material and the surface state of the radiation changes, that is, the emissivity, which is defined as the actual object and the same temperature blackbody radiation properties of the ratio. Object radiation and absorption of infrared radiation law to meet Kirchhoff's law, when a beam of radiation projected onto the surface of any object, according to the principle of conservation of energy, the object of incident radiation absorption rate, reflectivity, transmittance of the three must be equal to the sum of 1, the general emissivity is not easy to determine, usually through the measurement of the absorption rate to determine the emissivity, so the blackbody source of radiation as a radiation standard for checking a variety of infrared radiation source Radiation intensity.
Infrared thermometer by the optical system, photodetector, signal amplifier and signal processing, display output and other components. The measured object and the reflection of the source of the radiation line by the modulator demodulation input to the infrared detector. The difference between the two signals is amplified by the inverse amplifier and controls the temperature of the feedback source, so that the spectral radiation brightness of the feedback source is the same as the spectral radiation brightness of the object. The display indicates the brightness temperature of the object being measured. Infrared thermometer temperature measured by the object's radiation temperature rather than the actual temperature of the object, due to the absolute black body does not exist, at the same temperature in the actual object thermal radiation is always smaller than the total amount of radiation from the absolute black body, so the infrared thermometer measured temperature should certainly be less than the real temperature of the object. Temperature measurement should be as far as possible to set the infrared thermometer emissivity (for adjustable emissivity of the infrared thermometer) into the same emissivity value of the emissivity of the material being measured, as far as possible to make the measurement of the value of the real temperature of the object to be measured the same.
Infrared thermometer is now widely used, has become an important tool for detecting defects in electrical equipment. As a result of long-term use in the production line, on-site testing of substations, electrical equipment outlet joints, T-type wire clips, through the wall casing joints, bus nodes, knife gate cutter, cable joints; transmission lines, wire connecting tube, wire clips or wire connections. Due to the poor field use environment and improper routine maintenance may cause the operation of the infrared thermometer can not be accurately measured or even equipment failure, resulting in measurement inaccuracies, affecting the safe and stable operation of the power grid. In this paper, according to the principle of infrared temperature measurement in the operation of infrared thermometer self-calibration method, simple and easy to use, the use of units can be based on this method of self-calibration equipment, in the field before the test of infrared thermometer self-calibration comparison, to determine whether the infrared thermometer is in a good state of work, you can carry out the test work, in order to reduce the safety hazards.
