A flowmeter is an instrument used to measure fluid flow, which is widely used in industrial production, environmental monitoring, energy management and other fields. According to different principles and application scenarios, flowmeters can be divided into many types.
1.Doppler Ultrasonic Flowmeter:
The working principle of a Doppler ultrasonic flowmeter is mainly based on the Doppler effect, that is, when one object (such as the transmitter and receiver of ultrasound) moves at a relative speed with another object (such as the source of ultrasound), the frequency of the ultrasonic wave received by the receiver will be different from the frequency emitted by the transmitter. This difference in frequency is directly proportional to the relative velocity of the object, so the flow velocity of the object can be estimated by measuring this frequency difference.
The Doppler ultrasonic flowmeter is mainly composed of three parts:
Emitter: Generates ultrasonic waves and sends them into the fluid.
Receiver: Receives ultrasound waves scattered back by particles or bubbles in the fluid.
Signal Processor: Analyzes the received ultrasonic frequency changes and calculates the flow rate of the fluid based on the Doppler effect.
In the case of normal flow, the speed at which sound waves travel in the fluid is constant. But when there is a difference in fluid velocity, the frequency of the ultrasound changes. Based on this change in frequency, the flow rate of the fluid can be calculated.
Doppler ultrasonic flowmeters are widely used in the field of flow measurement due to their accuracy, reliability and ease of operation.
2.Radar Flow Meter:
Radar velocity meter is made by using the principle of Doppler effect, electromagnetic waves occur to the water surface when working, electromagnetic waves will scatter when encountering the moving water surface, and constitute an echo, because the received echo frequency is offset from the transmitting frequency to a certain extent, the water surface flow velocity can be obtained by the Doppler frequency equation, and a moving target will produce a low-frequency output signal in the radar sensor. The frequency of this signal depends on the speed of movement, and the amplitude depends on the distance of installation, reflectivity, and the size of the moving target. The Doppler frequency f is directly proportional to the speed of motion. The system of fixed-point radar velocity meter can be connected to multiple radar probes, which is equivalent to laying multiple measurement perpendicular lines, combining cross-section parameters, calculating cross-section flow, fixed-point measurement, and is suitable for flood detection, river flow monitoring, channel flow monitoring, drainage flow monitoring and other scenarios.
3.Mechanical Flow Meter:
Mechanical flowmeters are one of the earliest types of flow meters that work by measuring the pressure difference or rotating mechanical parts as a fluid passes through a pipe. Common mechanical flowmeters include orifice plate flowmeters, turbine flowmeters and liquid column flowmeters. These flowmeters have the characteristics of simple structure and high reliability, but they have high requirements for the nature and flow state of the fluid.
4.Electromagnetic Flowmeter:
An electromagnetic flowmeter is a flowmeter that uses the principle of Faraday electromagnetic induction to measure the flow rate of conductive liquids. When a conductive liquid passes through an electromagnetic flowmeter, the current in the liquid is proportional to the velocity in the perpendicular direction of the magnetic field, and the flow rate is determined by measuring the magnitude of the current in the liquid. Electromagnetic flowmeter has the advantages of wide measurement range, high accuracy, and is not affected by factors such as fluid density and viscosity, and is widely used in chemical industry, water treatment and other fields.
5.Ultrasonic Flow Meter:
Ultrasonic flowmeter is a flowmeter that uses the principle that the speed of ultrasonic waves propagating in a fluid is proportional to the flow rate. Ultrasonic flowmeters can be divided into two types: transfer time type and Doppler type. Transfer-time ultrasonic flowmeters determine the flow rate by measuring the time it takes for ultrasonic waves to propagate through the fluid, while Doppler ultrasonic flowmeters determine the flow rate by measuring the frequency change of ultrasonic waves in the fluid. Ultrasonic flowmeters are non-invasive, non-pressure loss, and suitable for various fluids, and are widely used in petroleum, chemical, heating and other industries.
6.Thermal Flow Meter:
A thermal flow meter is a flow meter that measures the flow rate by using the principle that the heat taken away by the fluid as it flows through the sensor is proportional to the flow rate. A thermal flow meter typically consists of two temperature sensors, a heating sensor and a measurement sensor. The heating sensor heats the fluid, the measurement sensor measures the change in the temperature of the fluid, and the flow rate is determined by measuring the temperature difference. Thermal flow meters are suitable for low-velocity, high-viscosity fluid measurements, and are commonly used for flow measurement of liquids and gases.
The above are some common types and principles of flowmeters, and with the development of science and technology, more new types of flowmeters will appear. Different types of flow meters are suitable for different fluids and application scenarios, and choosing the right flow meter is of great significance to accurately measure flow and improve production efficiency.