A flow meter is an instrument used to measure the flow of fluids such as liquids, gases, and steam. Its working principle and application fields are very wide, such as in chemical, petroleum, natural gas, pharmaceutical, food and beverage and other industries. This article will introduce the basic principles and classification of flow meters to help readers better understand flow meters.1. Basic principles of flow meters

Different types of flow meters work differently, but the basic principle of all flow meters is to calculate the flow rate by measuring the difference in velocity and/or pressure of the fluid passing through the measuring cell.

The basic principle of a flow meter is to measure the speed or flow of fluid through a pipe. Generally, flow meters can be divided into two types: volume flow meters and mass flow meters.

Volumetric flow meters calculate flow based on measuring the volume of fluid moving through a pipe. The simplest volumetric flow meter is a pipe. When liquid or gas passes through the pipe, the flow rate can be calculated based on the cross-sectional area of ​​the pipe and the speed of the fluid passing through the pipe. However, this method is not practical because in practical applications, both the cross-sectional area of ​​the pipe and the velocity of the fluid passing through the pipe vary. Therefore, volume flow meters usually use some special sensors to measure the speed or flow rate of fluid through the pipe, and use the flow rate and pipe cross-sectional area to calculate the flow rate.

Mass flow meters calculate flow based on measuring the mass of the fluid. Mass flow meters usually use some special sensors to measure the mass or density of a fluid and combine it with the velocity of the fluid and the cross-sectional area of ​​the pipe to calculate the flow rate. Mass flow meters are commonly used in applications where accurate measurement of fluid mass is required, such as in the chemical and petroleum industries.

2. Classification of flow meters

1. electromagnetic flow meter

The electromagnetic flow meter is a volumetric flow meter that measures the flow of liquid in conductive pipes based on the principle of electromagnetic induction. When the liquid passes through the conductive pipe, the liquid moves in the magnetic field as a conductor, and the magnetic field induces an electromotive force to generate a voltage, which is proportional to the liquid flow rate. Electromagnetic flow meter are mainly used to measure the flow of liquids, such as tap water, beverages, petroleum and chemicals.

2. vortex flow meter

A Vortex flow meter is a volumetric flow meter that uses the frequency of vortices formed around objects with resistance when the liquid flows to measure the flow rate of the liquid. When liquid passes through a Vortex flow meter, vortices are formed around the sensor, and the sensor converts the frequency of each Vortex into flow data. Vortex flow meters are mainly used to measure the flow of liquids, such as water, petroleum and chemicals.

3. turbine flow meter

A turbine flow meter is a volumetric flow meter that uses the speed of liquid through a rotating turbine to measure flow. When liquid passes through a turbine flow meter, the flow of liquid causes the turbine to rotate, and the speed of the turbine rotation is proportional to the flow rate. Turbine flow meters are mainly used to measure the flow of liquids, such as water, petroleum and chemicals.

4. Coriolis mass flow meter

Coriolis mass flow meter is a mass flow meter that uses the principle of Coriolis force to measure the flow of gas. When gas passes through a Coriolis mass flow meter, the gas flowing through the sensor is placed in a rotating magnetic field. The magnetic field induces a voltage signal that is proportional to the flow rate of the gas. Coriolis mass flow meters are mainly used to measure the flow of gases, such as air, oxygen and nitrogen.

5. gas mass flow meter

A gas mass flow meter is a flow meter specially used to measure gas mass flow. Unlike volume flow meters, gas mass flow meters do not need to measure gas volume or density, but directly measure the mass flow rate of gas. Therefore, gas mass flow meters are often used to measure the flow of variable density or compressible gases.

The working principle of gas mass flow meter is based on the law of conservation of mass and the principle of thermodynamics. Normally, gas will be subject to certain constraints and heating when flowing through the gas mass flow meter, resulting in temperature changes, which will affect the density of the gas. Therefore, the gas mass flow meter measures the temperature change before and after the gas flows through the equipment, and calculates the mass flow rate of the gas based on the principles of thermodynamics.

Gas mass flow meters usually consist of a sensor, calculator and display. Sensors usually include temperature sensors and mass flow sensors, which are used to measure temperature changes and mass flow of gases. The calculator is used to process the data collected by the sensor and calculate the mass flow rate of the gas according to the preset algorithm. The display is used to display the mass flow value of the gas.