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 radiation pyrometers.
The temperature measurement range and performance of radiation pyrometers are the same as those of optical pyrometers.

The measurement error of radiation pyrometer mainly comes from:
① The selective absorption of the intermediate medium (such as the atmosphere, etc.) makes the infrared part of the radiant energy reaching the receiver lose more;
② The distance from the heat source to the pyrometer is not measured (usually each radiation pyrometer specifies a ratio between the diameter of the observed surface area and the distance between the pyrometer lenses);
③ The selective absorption characteristics of the receivers in various pyrometers are different, which causes the spectral emissivity to deviate from the selected value; ④ The temperature changes of the hot and cold ends of the thermopile, the error of the instrument, etc.