Definition
The Far Infrared Thermometer is a non-contact temperature measuring instrument that detects the far infrared energy radiated from the surface of an object and converts it into a temperature reading. It is a common form of infrared thermometer, which is widely used in many non-medical fields such as industrial maintenance, food processing, environmental monitoring, and scientific research experiments due to its convenient operation and rapid response.
Principle
Far infrared thermometers work based on the law of black-body radiation. Any object with a temperature above absolute zero will radiate infrared energy outward, and its radiation intensity and wavelength distribution depend on the surface temperature of the object. The optical system of the thermometer gun collects the infrared radiation emitted by the target object and focuses it onto the infrared detector. The detector converts the radiation signal into an electrical signal, which is finally displayed as a temperature value after signal processing and temperature calibration. The process follows Stephen Boltzmann's law, which states that the radiated power of an object is proportional to the fourth power of its surface temperature, mathematically expressed as:
E = εσT4
where E is the radiant emissivity, ε is the surface emissivity, σ is the Stephen-Boltzmann constant, and T is the absolute temperature.
Measurement method
When using a far-infrared thermometer, make sure that the target is full of field of view, and it is usually recommended that the target size be larger than the spot diameter. Keep the temperature gun perpendicular to the surface to be measured during operation, reducing the error introduced by the measurement angle. Most instruments offer both single-point and continuous measurement modes, which can be selected according to the user's needs. The correct emissivity parameters should be set before measurement, and interference such as environmental reflection and atmospheric absorption should be compensated. Regular calibration with standard blackbody sources maintains the reliability of measurement results.
Influencing factors
Measurement accuracy is influenced by various factors. The emissivity of the object surface is a key parameter, and the emissivity of different materials varies greatly, and the wrong setting will lead to significant deviations. Strong light sources and high-temperature radiation sources in the environment may cause interference. The relationship between the measurement distance and the spot size should be in accordance with the distance factor ratio specified by the instrument. Water vapor and dust in the air have an absorption effect on infrared radiation, especially in long-distance measurements. In addition, the degree of oxidation, roughness and color of the measured surface will also have a certain impact on the emissivity.
Application:
In the industrial field, far-infrared temperature measuring guns are used to monitor the operating temperature of electrical equipment contacts and bearings to prevent overheating failures. In food processing, the temperature distribution of cooking and cooling processes can be monitored. It is often used in laboratories for material heat treatment research and chemical reaction temperature tracking. In the construction industry, it is used to test the thermal insulation performance and energy loss of walls. In agricultural research, it can be used for plant canopy temperature monitoring. These applications demonstrate the benefits of non-contact, fast measurement.
Selection
The measurement range should be considered when selecting to ensure that the expected temperature range is covered. The temperature resolution and accuracy should meet the specific application requirements. Optical resolution is determined by the distance factor ratio, and high ratios are suitable for small targets or long-distance measurements. Response time is important in dynamic temperature measurements. Adjustable emissivity range and preset material modes improve applicability. Environmental tolerance includes operating temperature range and degree of protection. The data logging function and output interface can be selected according to the data processing needs. Compliance with relevant international standards such as ASTM E1256 or GB/T 19146 can be regarded as a reference for product performance.