Infrared thermometer self-calibration error comparison method research
Because infrared thermometers have been used in production lines for on-site testing for a long time, the use environment is harsh, and daily maintenance is improper, it may cause infrared thermometers within the validity period of the calibration to be unable to measure accurately or even equipment failure, resulting in inaccurate measurements and affecting the safety and stability of the power grid. run. Based on the principle of infrared temperature measurement, the self-calibration method of the infrared thermometer in operation is studied. Users can use simple self-made equipment to conduct qualitative testing and analysis of the infrared thermometer at any time. The method is simple and easy to implement. Make sure the infrared thermometer is in good working condition and can measure accurately to reduce safety hazards.
With the development of modern technology, infrared thermometers are widely used in power line inspection, maintenance and substation operation work to detect temperature abnormalities in power equipment, distribution equipment, cables, electrical joints, etc. under operating and live conditions, and find 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 work quality and ensure safety, self-calibration of infrared thermometers must be carried out to ensure that the running infrared thermometers are in good working condition.
Blackbody Radiation and Infrared Thermometry Principles
All objects with a temperature higher than absolute zero are constantly emitting infrared radiation energy into the surrounding space. The size of the infrared radiation energy of an object and its distribution by wavelength are closely related to its surface temperature. Therefore, by measuring the infrared energy radiated by the object itself, the optical system of the thermometer is converted into electrical energy on the detector. The signal and the display part of the infrared thermometer display the surface temperature of the object being measured, and its surface temperature can be accurately measured. This is the objective basis on which infrared radiation temperature measurement is based.
Features of infrared thermometer: non-contact measurement, wide temperature measurement range, fast response speed, and high sensitivity. However, due to the emissivity of the measured object, it is almost impossible to measure the true temperature of the measured object. What is measured is the surface. temperature.
The standardized calibration method for infrared thermometers is to use blackbody furnace calibration. 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 is, the emissivity, is introduced that changes with the material properties and surface state. , 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 by an object satisfies Kirchhoff's law. When a beam of radiation is projected onto the surface of any object, according to the principle of conservation of energy, the sum of the object's absorption rate, reflectivity, and transmittance of the incident radiation Must be equal to 1. Generally, the emissivity is not easy to measure. The emissivity can usually be determined by measuring the absorption rate. Therefore, the blackbody radiation source is used as a radiation standard to test the radiation intensity of various infrared radiation sources.
Infrared thermometer consists 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 inverse amplifier and controls the temperature of the feedback source so that the spectral radiance of the feedback source is the same as the spectral radiance of the object. The display indicates the brightness temperature of the object being measured. 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 is always smaller than the total amount of absolute black body radiation at the same temperature, so infrared measurement The temperature measured by the thermometer should definitely be lower than the actual 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 material being measured, so that the measured value is as consistent as possible. The actual temperature of the object is consistent.
In the process of discussing the working principle of infrared thermometers and comparing self-calibration errors, I have mastered a lot of infrared knowledge, understood the process and methods of power infrared diagnosis, and studied the emissivity and distance coefficient of infrared thermometers. The influence of other parameters on the test results enables technicians to master the correct use and maintenance methods of infrared thermometers. Through the comparative study of self-calibration errors of infrared thermometers, the company's internal self-calibration specifications were formulated and implemented with approval. This calibration method has been promoted and applied within the company, improving the measurement supervision and management of infrared thermometers. This method can effectively detect infrared thermometer faults, ensure that the running infrared thermometer is in good working condition, ensure accurate and reliable value transmission, improve the safety factor, and ensure work quality.
