The Working Principle Of Infrared Thermometer

Features

In the production process, infrared temperature measurement technology plays an important role in product quality control and monitoring, equipment online fault diagnosis and safety protection, and energy-saving. In the past 20 years, non-contact infrared thermometers have developed rapidly in technology, with continuous improvement in performance, continuous enhancement of functions, continuous increase in varieties, continuous expansion of the scope of application, and market share increasing year by year. Compared with contact temperature measurement methods, infrared temperature measurement has the advantages of fast response time, non-contact, safe use, and long service life. Non-contact infrared thermometers include three series: portable, online and scanning, and are equipped with various options and computer software. In each series, there are various models and specifications. Among various types of thermometers with different specifications, it is very important for users to choose the correct infrared thermometer model.

Technical characteristics

Infrared detection technology is a key promotion project of national scientific and technological achievements in the "Ninth Five-Year Plan". Any object will continuously radiate infrared heat energy due to the movement of its own molecules, thereby forming a certain temperature field on the surface of the object, commonly known as "thermal image". Infrared diagnostic technology is precisely by absorbing this infrared radiation energy to measure the temperature of the surface of the device and the distribution of the temperature field, thereby judging the heating of the device. There are many test equipment using infrared diagnostic technology, such as infrared thermometers, infrared thermal televisions, infrared thermal imaging cameras, and so on. Devices such as infrared thermal televisions and infrared thermal imaging cameras use thermal imaging technology to convert this invisible "thermal image" into visible light images, which makes the testing effect intuitive and highly sensitive and can detect subtle changes in the thermal state of the device and accurately reflect it. The heating conditions inside and outside the equipment have high reliability and are very effective for detecting hidden dangers of the equipment.

Infrared diagnostic technology makes reliable predictions of early fault defects and insulation performance of electrical equipment and improves the preventive test and maintenance of traditional electrical equipment (preventive test is the standard introduced in the former Soviet Union in the 1950s) to the predictive state of maintenance, which is also modern power The direction of business development. In particular, the development of large units and ultra-high voltages has put forward higher and higher requirements for the reliable operation of the power system, which is related to the stability of the power grid. With the continuous development of modern science and technology, the use of infrared condition monitoring and diagnosis technology has the characteristics of long-distance, non-contact, non-sampling, non-disintegration, and is accurate, fast, and intuitive, real-time online monitoring and diagnosis of electrical equipment Most failures (almost can cover the detection of various failures of all electrical equipment). It has attracted much attention from the power industry at home and abroad (an advanced state maintenance system commonly used in the late 1970s abroad), and has been rapidly developed. The application of infrared detection technology is of great significance for improving the reliability and effectiveness of electrical equipment, improving operating economic benefits, and reducing maintenance costs. It is a good method commonly promoted in the field of predictive maintenance, and it can also raise the level of maintenance and the health of equipment to a higher level.

Infrared imaging detection technology can perform non-contact detection of running equipment, photograph the distribution of its temperature field, measure the temperature value of any part, and diagnose various external and internal faults based on this, with real-time, remote measurement, intuitive and quantitative The advantages of temperature measurement are very convenient and effective for detecting the operating equipment and live equipment of power plants, substations, and transmission lines.

The method of using a thermal imaging camera to detect online electrical equipment is the infrared temperature recording method. Infrared thermography is a new technology used in the industry for non-destructive detection, testing equipment performance, and mastering its operating status. Compared with traditional temperature measurement methods (such as thermocouples, wax slices with different melting points, etc. placed on the surface or body of the object to be measured), thermal imaging cameras can detect the temperature of the heating point at a certain distance in real time, quantitatively, and online. , It can also draw the thermal image of the temperature gradient of the equipment in operation, and the sensitivity is high, and it is not interfered with by the electromagnetic field, which is convenient for on-site use. It can detect thermally induced faults in electrical equipment with a high resolution of 0.05°C in a wide range of -20°C to 2000°C, revealing heat generated by wire connectors or clamps, and local hot spots in electrical equipment.

Infrared diagnosis technology of charged equipment is a new subject. It is a comprehensive technology that uses the heating effect of charged equipment and uses special equipment to obtain infrared radiation information from the surface of the equipment, and then judge the condition of the equipment and the nature of the defect.

Basic theory

In 1672, it was discovered that sunlight (white light) is composed of light of various colors. At the same time, Newton made the famous conclusion that monochromatic light is simpler in nature than white light. Using a light splitting prism, the sunlight (white light) is decomposed into red, orange, yellow, green, cyan, blue, purple, and other colors of monochromatic light. In 1800, the British physicist F. W. Huxel discovered infrared when he studied various colored lights from a thermal point of view. When he was studying the heat of various colors, he deliberately blocked the only window of the darkroom with a dark board and opened a rectangular hole in the board with a dichroic prism. When sunlight passes through the prism, it is broken down into colored light strips, and a thermometer is used to measure the heat contained in the different colors in the light strips. In order to compare with the ambient temperature, Huxel used a few thermometers placed near the colored light band as a comparison thermometer to measure the ambient temperature. During the experiment, he accidentally discovered a strange phenomenon: a thermometer placed outside the red light had a higher temperature rating than other indoor temperatures. After repeated trials, this so-called high-temperature zone with the most heat is always outside the red light at the edge of the light strip. So he announced that in addition to visible rays of radiation emitted by the sun, there is also a "hot wire" that is invisible to the human eye. This invisible "hot wire" is located outside of the red light and is called infrared light. Infrared is a kind of electromagnetic wave, which has the same essence as radio waves and visible light. The discovery of infrared is a leap in human understanding of nature, and it has opened up a new and broad road for the research, utilization, and development of infrared technology.

The wavelength of infrared is between 0.76~1000μm. According to the wavelength range, it can be divided into four types: near-infrared, mid-infrared, far-infrared, and extremely far-infrared. Its position in the continuous spectrum of electromagnetic waves is between radio waves and visible light. . Infrared radiation is one of the most widespread electromagnetic radiation in nature. It is based on the fact that any object will produce its own irregular movement of molecules and atoms in a normal environment, and constantly radiate thermal infrared energy, the movement of molecules and atoms. The more intense, the greater the radiated energy, and vice versa, the smaller the radiated energy.

Objects with a temperature above absolute zero will radiate infrared rays due to the movement of their own molecules. After the power signal radiated by the object is converted into an electrical signal by the infrared detector, the output signal of the imaging device can simulate the spatial distribution of the surface temperature of the scanned object in a one-to-one correspondence and is processed by the electronic system and transmitted to the display screen to obtain The corresponding thermal image of the heat distribution on the surface of the object. Using this method, it can realize the long-distance thermal image imaging and temperature measurement of the target, and analyze and judge it.