Principle and structure of infrared thermometer
Focus the infrared radiation received from the object being measured onto the detector through a lens and filter. The detector generates a current or voltage signal proportional to temperature by integrating the radiation density of the measured object. In the subsequent connected electrical components, this temperature signal is linearized, the emissivity region is corrected, and converted into a standard output signal.
In principle, there are two types of thermometers: portable thermometers and fixed thermometers. Therefore, when selecting a suitable infrared thermometer for different measurement points, the following characteristics will be the main ones:
1. Sight
The sight has this function. The measuring block or point pointed by the thermometer can be seen, and a large area of the object being measured can often be avoided without the sight. It is recommended to use a sight with instrument panel markings or laser pointing points in the form of a transparent mirror when measuring small objects and long distances.
2. Lens
The lens determines the measured point of the thermometer. For large objects, a thermometer with a fixed focal length is generally sufficient. But when measuring distance away from the focal point, the image at the edge of the measurement point will be unclear. For this reason, it is better to use a zoom lens. Within the given zoom range, the thermometer can adjust the measurement distance. The latest thermometer comes with a replaceable zoom lens, and the near and far lenses can be replaced without calibration and retesting.
3. Sensor, i.e. spectral receiver
Temperature is inversely proportional to wavelength. At low object temperatures, sensors sensitive to long wave spectral regions (such as hot film sensors or thermoelectric sensors) are suitable. At high temperatures, photoelectric sensors composed of germanium, silicon, indium gallium, etc. that are sensitive to short waves will be used.
