The working principle of common thermometers.

This article introduces five industrial common thermometers: liquid expansion thermometer, solid expansion thermometer, pressure thermometer, thermocouple thermometer, and thermal resistance thermometer.

1. Liquid expansion thermometer

Liquid expansion thermometers are manufactured based on the thermal expansion and contraction properties of liquids.

The most common one is the glass tube liquid thermometer, which uses the principle that the volume of liquid in the glass tube expands as the temperature increases.

The liquid expansion thermometer consists of four parts: liquid storage, capillary tube, ruler, and safety bubble.

The liquid can be: mercury, alcohol, toluene, etc.

2. Solid expansion thermometer

Solid expansion thermometers are made of two materials with different expansion coefficients.

Common types include: rod thermometer (generally made of solid material with a large expansion coefficient), bimetal thermometer (its temperature sensing element is made of two metal sheets with different expansion coefficients firmly bonded together) .

Solid expansion thermometer has the advantages of simple structure and reliability, but its accuracy is low.

3. Pressure thermometer

A pressure thermometer is a mechanical instrument that uses the property of the pressure of the working medium in a closed volume to increase as the temperature increases, and determines the temperature value by measuring the pressure of the working medium.

The working medium of a pressure thermometer can be gas, liquid or steam. Pressure thermometers are simple and reliable, have good shock resistance, and have good explosion-proof properties. Therefore, they are often used on airplanes, cars, and tractors. They can also be used as temperature control signals. This type of thermometer has poor dynamic performance and large lag in the indication value, so it cannot be used for Measure rapidly changing temperatures.

4. Thermocouple thermometer

Thermocouple thermometer is a temperature measurement device widely used in industrial production.

Two conductors with different compositions (called thermocouple wires or hot electrodes) are connected at both ends to form a loop. When the temperatures at the junction are different, an electromotive force will be generated in the loop. This phenomenon is called the thermoelectric effect, and this The electromotive force is called thermoelectric potential. Thermocouples use this principle to measure temperature.

5. Resistance thermometer

As the temperature increases, the resistance of the conductor or semiconductor will change. There is a single functional relationship between temperature and resistance. The method of using this functional relationship to measure temperature is the thermal resistance temperature measurement method, which is used to measure temperature. The conductor or semiconductor is called a thermal resistor.

In summary, the above are five common thermometers. You must understand their working principles in advance to use them better and avoid accidents due to improper use. If you want to know more about machinery, you can log on to the BTMA website and contact Cindy WhatsApp: +8613674903170. I will give you the best machines and service.