Definition
An infrared thermal imager is a non-contact temperature measurement and imaging device that converts invisible infrared energy into visible thermal images by detecting infrared radiation emitted by the surface of an object. This equipment can intuitively display temperature distribution and is widely used in industrial testing, scientific research experiments, medical diagnosis and security monitoring and other fields.
Principle
Infrared thermal imagers work based on the law of blackbody radiation. All objects above absolute zero emit infrared radiation, the intensity of which correlates with the temperature of the surface of the object. The thermal camera's optical system collects infrared radiation and focuses it onto an infrared detector, which converts the radiated signal into an electrical signal, which is then processed to produce a color or grayscale image that reflects the temperature distribution. Among them, Planck's law of black-body radiation describes the relationship between radiation intensity and wavelength and temperature:
Mλ = (2πhc2/λ5) × [1/(ehc/λkT - 1)]
Here MλIt represents the degree of spectral radiation, h is Planck's constant, c is the speed of light, λ is the wavelength, k is the Boltzmann constant, and T is the absolute temperature.
Measurement method
When using an infrared thermal imager for measurement, the following steps are usually followed: First, set the appropriate emissivity parameters according to the characteristics of the object being measured, which is a key factor affecting measurement accuracy. Second, ensure a stable measurement environment and avoid strong airflow, reflective sources, or background radiation interference. Then, point the camera at the target area, adjusting the focal length to get a clear image. Finally, the temperature data is obtained through the analysis software, which can be used to analyze the temperature of points, lines, or areas, and generate a test report. The measurement process should refer to relevant industry standards, such as ASTM E1934.
Influencing factors
The measurement results of an infrared thermal camera are influenced by a variety of factors. The emissivity of the surface of the object is the main factor, and the emissivity of different materials varies greatly, which needs to be corrected according to the material properties. Environmental conditions such as air temperature, humidity, and airflow can affect heat conduction, altering surface temperature distribution. The measurement distance and viewing angle also affect the spatial resolution and temperature measurement accuracy. In addition, background heat radiation, reflection and atmospheric absorption may introduce errors that need to be compensated for by instrument settings or data processing.
Applications
In the industrial field, infrared thermal imaging cameras are commonly used for overheating detection of electrical equipment, mechanical fault diagnosis, and building energy conservation assessment. In scientific research experiments, it can be used for thermal property analysis, fluid mechanics research, and biothermal imaging. In terms of medical care, thermal imaging cameras assist in inflammation screening and blood circulation assessment. In security monitoring, it is used for night monitoring and fire warning. Applications in various industries need to be combined with appropriate standards, such as NFPA 70B for electrical testing and ISO 6781 for building testing.
Selection considerations
When choosing an infrared thermal imager, it is necessary to comprehensively consider the technical parameters and application requirements. The type and resolution of the detector determine the details of the image, and the common ones are uncooled and cooled. The temperature measurement range should cover the possible temperature of the target object. Thermal sensitivity reflects the instrument's ability to distinguish between small temperature differences. Spatial resolution and field of view affect the size and distance of the target that can be detected. In addition, data interfaces, software functions, and environmental adaptability need to be considered. It is recommended to refer to the performance requirements in standards such as IEC 80601-2-59 for specific application scenarios.