There are many kinds of thermometers, which are divided into civil and industrial use, and there are also many kinds of products. The industry has main products such as thermal resistance, thermocouple, bimetal thermometer, temperature transmitter, and digital display thermometer. Common temperatures are: -100 degrees, 200 degrees, 500 degrees, 800 degrees, 1200 degrees, 1600 degrees, 1800 degrees, or even higher, depending on your needs.

According to the difference of the purpose of use, a variety of thermometers have been designed and manufactured. Its design is based on: the use of the phenomenon of thermal expansion and contraction of solids, liquids and gases under the influence of temperature; under the condition of constant volume, the pressure of gas (or vapor) changes due to the difference of temperature; the role of thermoelectric effect; Changes in temperature; the influence of thermal radiation, etc.
For non-contact high-temperature measuring instruments, when the measured temperature is higher than the range that thermocouples can use, and where thermocouples cannot be installed or are not suitable for installation, optical pyrometers can generally meet this requirement. It is widely used to measure the temperature of smelting, casting, steel rolling, glass furnace, forging, heat treatment, etc. It is one of the temperature measuring instruments required in metallurgy, and machinery and other industrial processes.