Research on the Self-calibration Error Comparison Method for Infrared Thermometers
Abstract: Due to the long-term use of infrared thermometers in the production line for on-site testing, the use of harsh environments, and improper daily maintenance, the infrared thermometers within the validity period of the verification may not be able to measure accurately or even equipment failures, resulting in inaccurate measurements and affecting the power grid. Safe and stable operation. According to the principle of infrared temperature measurement, the self-calibration method of infrared thermometer in operation is studied. Users can use simple self-made equipment to carry out qualitative test and analysis of infrared thermometer at any time. The method is simple and easy. Ensure that the infrared thermometer is in good working condition, measure accurately, and reduce potential safety hazards.
With the development of modern technology, infrared thermometers are widely used in power line inspection, maintenance and substation operation, to detect abnormal temperatures of power equipment, power distribution equipment, cables, electrical connectors, etc. under operating and electrified conditions, and found that Defects in electrical equipment. Whether the infrared thermometer in use is in good working condition directly affects the safe and stable operation of the power grid. In order to improve the quality of work and ensure safety, self-calibration of infrared thermometers must be carried out to ensure that the infrared thermometers in operation are in good working condition.
Black body radiation and the principle of infrared temperature measurement
All objects with a temperature higher than absolute zero are constantly emitting infrared radiation energy to the surrounding space. The size of the infrared radiation energy of an object and its distribution according to the wavelength have a very close relationship with its surface temperature. Therefore, through the measurement of the infrared energy radiated by the object itself, the optical system of the thermometer is converted into an electric sensor on the detector. Signal and through the display part of the infrared thermometer to display the surface temperature of the measured object, it can accurately measure its surface temperature, which is the objective basis for infrared radiation temperature measurement.
Features of infrared thermometer: non-contact measurement, wide temperature measurement range, fast response speed, high sensitivity, but due to the influence of the emissivity of the measured object, it is almost impossible to measure the real temperature of the measured object, the measurement is the surface temperature.
The standardized verification method of infrared thermometer is to use black body furnace verification. A black body refers to an object whose absorption rate of incident radiation of all wavelengths is equal to 1 under any circumstances. A black body is an idealized object model, so a radiation coefficient that varies with material properties and surface states is introduced, that is, the emissivity , which is defined as the ratio of the radiation performance of an actual object to that of a blackbody at the same temperature. The law of radiation and absorption of infrared radiation of an object satisfies Kirchhoff's law. When a beam of radiation is projected onto the surface of any object, according to the principle of energy conservation, the sum of the object's absorptivity, reflectivity, and transmittance to the incident radiation It must be equal to 1. Generally, the emissivity is not easy to measure. Usually, the emissivity can be determined by measuring the absorptivity. Therefore, the black body radiation source is used as a radiation standard to verify the radiation intensity of various infrared radiation sources.
The infrared thermometer is composed of optical system, photoelectric detector, signal amplifier, signal processing, display output and other parts. The radiation from the measured object and the reflection source is demodulated by the modulator and then input to the infrared detector. The difference between the two signals is amplified by the anti-amplifier and controls the temperature of the feedback source, so that the spectral radiance of the feedback source is the same as that of the object. The display indicates the brightness temperature of the measured object. The temperature measured by the infrared thermometer is the radiation temperature of the object rather than the actual temperature of the object. Since the absolute black body does not exist, the total amount of thermal radiation of the actual object at the same temperature is always smaller than the total amount of absolute black body radiation, so the infrared measurement The temperature measured by the thermometer should definitely be lower than the real temperature of the object. When measuring temperature, the emissivity of the infrared thermometer should be set as much as possible (for infrared thermometers with adjustable emissivity) to the same emissivity value as the measured material, so that the measured value is as close as possible to the measured value. The actual temperature of the object is the same.
Infrared thermometers are now widely used and have become an important tool for detecting defects in electrical equipment. Due to long-term use in the production line, on-site testing of electrical equipment outlet connectors, T-shaped clamps, wall bushing connectors, busbar nodes, knife gates, cable connectors in substations; wire connection pipes, wire clamps or wire connections for transmission lines waiting. Due to the harsh on-site use environment and improper daily maintenance, the infrared thermometer in operation may not be able to measure accurately or even equipment failure, resulting in inaccurate measurement and affecting the safe and stable operation of the power grid. This paper studies the self-calibration method of the infrared thermometer in operation according to the principle of infrared temperature measurement. It is simple and easy. The user can make self-calibration equipment according to this method. Whether the infrared thermometer is in good working condition can be tested to reduce potential safety hazards.
