An overview of the research on the method of self-calibration error misalignment of infrared thermometers
With the development of modern technology, infrared thermometer is widely used in power line inspection, maintenance and substation operation work, in the operation and charged conditions to detect power equipment, power distribution equipment, cables, electrical connectors and other temperature anomalies, and find electrical equipment defects. The use of infrared thermometer working condition is good, directly affecting the stable operation of the power grid. In order to improve the quality of work, to ensure safety, infrared thermometer must be carried out since the calibration work to ensure that the operation of the infrared thermometer is in good working condition.
1 black body radiation and infrared temperature measurement principle
All temperatures higher than zero degrees 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 basis of infrared radiation thermometry 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 standardised calibration method for infrared thermometers 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 idealised model of the object, so the introduction of a radiation coefficient with the nature of the material and the state of the surface changes, i.e., 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 and the sum of the three must be equal to 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 the determination of a variety of sources of infrared radiation 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, because the 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 black body, so the infrared thermometer temperature measured by the object should certainly be smaller than the real temperature. Temperature measurement should be as far as possible to set the infrared thermometer emissivity (for the adjustable emissivity of the infrared thermometer) into the same emissivity value of the emissivity of the material to be measured, as far as possible to make the measurement of the value of the real temperature of the object to be measured.
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 of the environment as well as 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 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 the 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 security risks.
