There are many types of temperature measurement methods in the industry. According to the temperature measurement methods, they can be divided into two categories: contact temperature measurement and non-contact temperature measurement.
According to the principle of temperature measurement, contact temperature measurement instruments can be classified into three categories: expansion type, thermal resistance, and thermocouple; non-contact temperature measurement instruments mainly refer to radiation temperature measurement.

Expansion thermometers can be divided into: solid thermal expansion type (bimetal thermometer), liquid thermal expansion type (glass liquid thermometer), and gas thermal expansion type (pressure thermometer).
Thermal resistance can be further divided into metal thermal resistance (platinum thermal resistance, copper thermal resistance) and semiconductor thermal resistance (germanium, carbon, metal oxide thermistor).
Thermocouples can be divided into metal thermocouples and refractory metal thermocouples.
Thermometers based on the radiation measurement principle can be divided into radiation pyrometers, optical pyrometers and colorimetric pyrometers.