Thermocouple Thermometer
Working principle: Thermocouples use this principle to measure temperature. One end that is directly used to measure the temperature of the medium is called the working end, also called the measuring end, and the other end is called the cold end, also called the compensation end; the cold end and the display instrument Or connected with a matching instrument, the display instrument will indicate the thermoelectric potential generated by the thermocouple.
Features: ①High measurement accuracy. Because the thermocouple is in direct contact with the measured object, it is not affected by the intermediate medium; ② the measurement range is wide. Commonly used thermocouples can be continuously measured from -50°C to +1600°C, and some special thermocouples can be measured at a minimum of -269°C and a maximum of +2800°C; ③The structure is simple and easy to use. It is usually composed of two different metal wires, and is not limited by size and shape, and has a protective sleeve outside, which is very convenient to use.

Optical Pyrometer
Working principle: Use the relationship between the brightness and temperature radiated by the heat source to measure high temperature. The relationship between the actual temperature T of the object and the brightness temperature Ts can be obtained from the law of energy distribution of thermal radiation.
Working characteristics: generally measure objects with a temperature greater than 500 ℃. This thermometer is mainly made of a telescope equipped with a red filter and a set of circuits with a small bulb, a galvanometer and a variable resistor. Before use, establish the relationship between the temperature corresponding to the different brightness of the filament and the reading on the galvanometer. When in use, align the telescope with the object to be measured, adjust the resistance, so that the brightness of the bulb is the same as that of the object to be measured, then the temperature of the object to be measured can be read from the galvanometer.