Thermocouple thermometer: It is a temperature measuring instrument widely used in industry. Made using thermoelectric phenomenon. Two different wires are welded together to form the working end, and the other two ends are connected to the measuring instrument to form a circuit.

Put the working end at the temperature to be measured. When the temperature of the working end is different from that of the free end, an electromotive force will appear, so a current will flow through the circuit. Through the measurement of electrical quantities, the temperature at another place can be determined by using the temperature at a known place.
It is suitable for two substances with large temperature difference, and is mostly used for high temperature and low turbidity measurement. Some thermocouples can measure high temperatures as high as 3000°C, and some can measure low temperatures close to absolute zero.
Resistance thermometers: divided into metal resistance thermometers and semiconductor resistance thermometers, both of which are made according to the characteristic that the resistance value changes with temperature. Metal thermometers are mainly made of pure metals such as platinum, gold, copper, nickel, and alloys of rhodium iron and phosphor bronze. Semiconductor thermometers mainly use carbon, germanium, etc. Resistance thermometers are easy to use and reliable, and have been widely used. It has a measuring range of -260°C to around 600°C.