Instruments that measure higher temperatures. The most important are optical pyrometers and ir pyrometers. In the optical pyrometer, the filament is heated to the calibrated heat, and compared with the color of the high-heat object, the heat of the filament is adjusted so that the color is consistent with the high-heat object, and the temperature of the filament is the temperature of the high-heat object. In the radiation pyrometer, the radiation from the object is concentrated on the thermopile, and the corresponding voltage is generated according to the amount of thermal radiation intercepted, and then the voltage is converted into the temperature of the object.

Pyrometers come in two forms:
1) A device for measuring the temperature of a molten pool, comprising: a refractory mounting sleeve and an optical pyrometer;
2) Generally refers to the thermometer used to measure the temperature higher than 500℃. Commonly used pyrometers include optical pyrometers, colorimetric pyrometers and ir pyrometers.
In addition, thermocouple thermometers can also be used to measure high temperatures below 3000°C. But because the measuring range of thermocouple thermometer can be as low as -200 ℃, it is generally not classified as a pyrometer.