The infrared rays received from the measured object are focused on the detector by the lens through the filter. The detector generates a current or voltage signal proportional to the temperature by integrating the radiation density of the measured object. In the electrical components connected thereafter, the temperature signal is linearized, the emissivity area is corrected, and converted into a standard The output signal.

In principle, there are two types of infrared pyrometers: portable pyrometers and fixed pyrometers. Therefore, when choosing a suitable infrared pyrometer for different measurement points, the following features will be the main ones:

1. Sight
The sight has this function, the measuring block or measuring point pointed by the infrared pyrometer can be seen, and the sight can be often not needed for a large area of ​​the object to be measured. In the case of a small object to be measured and a long measuring distance, it is recommended that the sight is equipped with a dashboard scale or laser pointer in the form of a translucent mirror.

2. Lens
The lens determines the measured point of the pyrometer. For large-area objects, an infrared pyrometer with a fixed focal length is generally sufficient. But when the measurement distance is far away from the focus 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 pyrometer can adjust the measuring distance. The latest pyrometer has a zoom lens replaceable. The near lens and the far lens can be replaced without calibration and recheck.

3. The sensor, that is, the spectral receiver
Temperature is inversely proportional to wavelength. At low object temperatures, sensors that are sensitive to the long-wave spectral region (thermal film sensors or pyroelectric sensors) are very suitable. At high temperatures, short-wave sensitive sensors are used, consisting of germanium, silicon, indium-gallium, etc. photoelectric sensor.

When selecting the spectral sensitivity, the absorption bands of hydrogen and carbon dioxide should also be considered. Within a certain wavelength range, the so-called "atmospheric window", H2 and CO2 are almost transparent to infrared rays. Therefore, the light sensitivity of the infrared pyrometer must be within this range to eliminate the influence of atmospheric concentration changes. When measuring thin films or glass, it must be considered that these materials are not easily penetrated within a certain wavelength. In order to avoid the measurement error caused by the background light, use a suitable sensor that only receives the surface temperature. Metal has this physical property, and the emissivity increases with the decrease of the wavelength. Based on experience, when measuring the temperature of the metal, the shortest is generally selected The measurement wavelength.