Many times, we are not only concerned about the surface temperature of an object, but also want to understand its internal temperature distribution in order to conduct in-depth structural analysis and defect detection. Infrared imaging technology came into being, which can display the temperature distribution of an object in the form of intuitive images. Thermal imagers are based on this technical principle, capturing and converting the invisible infrared energy emitted by an object to generate visible thermal images. These images represent different temperatures of the measured object in different colors, thus providing us with a way to deeply understand the temperature distribution of the object. Next, we will briefly introduce the principles of thermal imaging under different imaging devices.
1. History of thermal imagers
Infrared thermal imagers are widely used in both military and civilian fields, such as infrared thermometers, infrared thermal imagers, and infrared alarms. Its history can be traced back to military use, and then gradually turned to civilian use, mainly serving in the fields of research and development, industrial testing and equipment maintenance, and also playing an important role in fire prevention, night vision and security.
The origin of infrared imaging technology can be traced back to the 1930s. At that time, the technology used alkali metal or semiconductor photocathode under high vacuum to convert infrared radiation into electronic radiation, and then converted the electronic image into an optical image visible to the naked eye through a fluorescent screen. However, due to the low sensitivity of early infrared image converters, observation often requires "active" irradiation of infrared radiation devices.
With the development of technology, low-light image enhancement technology and passive infrared thermal imaging technology have been introduced to solve the problems of poor concealment and bulky devices of active infrared night vision devices. In 1964, Texas Instruments provided the first military infrared thermal imaging system to the US military, marking a new stage of development of infrared thermal imaging technology.
Today, although military applications are still an important driving force for the development of infrared technology, its application in various fields of the national economy is also becoming increasingly widespread, such as industrial inspection, medical diagnosis, and satellite remote sensing. In particular, the successful application of uncooled focal plane technology has made the new generation of infrared temperature measurement thermal imagers more advanced in technical performance and more convenient to operate.
The research and application of domestic infrared technology started in the late 1950s, and initially mainly served the national defense cause. After decades of accumulation and breakthroughs, the military and high-tech fields have become a bright stage for my country's infrared technology. With the deepening of reform and opening up, military infrared technology has gradually shifted to the civilian field. Today, the research, development, production and improvement of domestic infrared thermal imagers are in a new stage. The rapid progress of electronic technology and the introduction of foreign advanced technology have made domestic infrared thermal imagers significantly improved in function, temperature measurement accuracy and practicality, and some indicators have even reached the world's leading level.
Next, let us take a closer look at the working principle of thermal imagers. Modern thermal imagers rely on infrared detectors and optical imaging lenses to capture and measure radiation, and then link radiation to the surface temperature of objects. Any object above absolute zero will emit infrared radiation, and thermal imagers collect these radiations through their infrared optical systems. These radiations are converted into electrical signals by infrared detectors, and then amplified and processed, and finally presented through photosensitive elements. Infrared thermal images visible to the human eye, the image directly reflects the heat distribution on the surface of the object.
Figure 2 shows the principle block diagram of the infrared thermal imager, which mainly consists of five parts: first, the infrared lens, which receives and gathers the infrared radiation emitted by the object under test; then the infrared detector component, which is responsible for converting the received thermal radiation signal into an electrical signal; then, the electronic component processes these electrical signals accordingly; then, the display component converts the processed electrical signal into an optical image visible to the naked eye; finally, the software part is responsible for in-depth processing of the collected temperature data, and finally presents it as a temperature reading and image.
III. Application of thermal imagers
The application field of infrared thermal imagers is expanding as people gain a deeper understanding of it. This instrument can quickly detect poor contact and overheated mechanical parts of electrical equipment, thereby preventing potential short circuits and fire risks. It can not only intuitively display the temperature distribution of the equipment, but also discover the thermal hazards of those shielded parts through heat conduction. In terms of operation testing, infrared thermal imaging products perform well, whether it is a circuit breaker, conductor, busbar or other components, it can easily cope with it. In addition, it can effectively detect circuit overload or unbalanced state of three-phase load.
In the field of predictive maintenance, infrared thermal imagers play a vital role. By conducting infrared thermal imaging inspections on all electrical equipment and power distribution systems, potential thermal hazards can be detected and handled in a timely manner, effectively preventing accidents such as fires and shutdowns. Special attention should be paid to key facilities such as various electrical devices, transformers, motors and generators, which may cause serious consequences such as arcs, short circuits, burns and fires. Through the inspection of infrared thermal imaging products, these hazards can be discovered and handled in a timely manner to ensure the safe and stable operation of the facilities.
Figure 4: Diversified applications of thermal imagers
Thermal imagers have demonstrated their excellent effectiveness in many fields. Whether it is electrical equipment maintenance inspection, roof leak detection, energy-saving detection, environmental protection inspection, or security and anti-theft, forest fire prevention, or even non-destructive testing, quality control and medical examinations, it can show its prowess. In the field of scientific research, thermal imagers also play an indispensable role, such as injection molding, mold temperature control, and electronic circuit design in automotive research and development. In addition, the motor and electronics industries also widely use thermal imagers for printed circuit board thermal distribution design and product reliability testing.
It is worth mentioning that infrared thermal imagers shine in security systems and become a star product for security monitoring. Its concealed detection function does not require visible light, making it difficult for criminals to detect their work location and existence, thereby increasing the risk of criminal behavior being discovered. In important units such as administrative centers, bank vaults, etc., 24-hour infrared thermal imaging monitoring combined with intelligent equipment processing can detect abnormalities in a timely manner and automatically process and report, thereby improving the level of monitoring.
4. How to choose a suitable thermal imager
Infrared thermal imagers are increasingly widely used in modern society, providing strong support for high-precision detection and monitoring. However, due to the high-tech content and price differences of products, choosing a suitable thermal imager has become a challenge. Users should focus on key indicators such as resolution, pixels, and frame rate according to their personal needs, and choose cost-effective equipment. At the same time, understanding the needs of specific application areas is also the key to choosing a suitable thermal imager.
3. Temperature measurement range
The temperature measurement range of an infrared thermal imager has a significant impact on its price and performance. The temperature measurement range should not only be wide, but also optional to provide more flexible applications. In most cases, the temperature measurement range of -20-120 degrees that we often use is sufficient to meet the high sensitivity requirements and help the equipment to measure accurately. Although the price is slightly higher, its outstanding performance in actual work and the many conveniences it brings are undoubtedly worth the money.
5. How to use infrared thermal imagers
With the popularity of infrared thermal imagers, more and more people are beginning to contact and use them. It is particularly important to master the correct usage methods and techniques. Here are some key points:
Clear requirements: Do you only need clear infrared thermal images, or do you also require accurate temperature measurement? Accurate temperature measurement requires more comprehensive information, such as emissivity, ambient temperature, etc., to ensure that the true temperature of the target object is accurately reflected.
Understand the maximum measurement distance: To ensure accurate temperature measurement, it is necessary to understand the maximum measurement distance at which the instrument can get accurate readings. The target image must occupy enough pixels for the instrument to accurately distinguish. Too far a distance may cause the target to be too small, affecting the accuracy of temperature measurement.
Choose a suitable temperature measurement range: Choose an appropriate temperature measurement range according to actual needs to ensure that the instrument can accurately measure and display the true temperature of the target object.
Following these usage methods and tips will help you better use infrared thermal imagers for high-precision inspection and monitoring.
4. Adjust the focal length
When using an infrared thermal imager, we can adjust the image curve after storing the infrared image, but it should be noted that the focal length cannot be changed after the image is stored, and other messy heat reflections cannot be eliminated. To ensure the correctness of the operation, the focal length should be carefully adjusted at the first time. When overheated or overcooled reflections above or around the target affect the measurement accuracy, you can try to adjust the focal length or measurement direction to reduce or eliminate these effects.
5. Single working background
When performing outdoor inspections in cold weather, you will find that most targets are close to the ambient temperature. To avoid the influence of solar reflection and absorption on the image and temperature measurement, it is a good idea to choose to measure at night. However, some older infrared thermal imagers may be limited to nighttime use.
6. Keep the instrument stable
During the shooting process, the movement of the instrument may cause blurred images. For best results, it is recommended to keep the instrument stable when freezing and recording images. When pressing the storage button, make sure the movement is gentle and smooth. Even the slightest shaking of the instrument may cause image quality degradation. To keep it stable, you can place the instrument on a surface or use a tripod.