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The working principle of electromagnetic flowmeter

Author:    Source:    Date: 2021-05-20 17:05:52
1. Working principle
Electromagnetic flowmeter is an instrument based on Faraday's law of electromagnetic induction, used to measure the volume flow of conductive liquids. But it cannot measure the flow of steam, gas and purified water. With its unique advantages, electromagnetic flowmeters are widely used in the flow measurement of various conductive liquids in industrial processes, such as various corrosive media such as sulfuric acid, alkali, industrial sewage, etc.;
2. Principle structure
The structure of electromagnetic flowmeter is mainly composed of measuring tube, electrode, shell, lining and converter, as shown in Figure 1.
Measuring tube: Its function is to let the measured conductive liquid pass through. In order to shunt or short-circuit the magnetic flux when the magnetic field lines pass through the measuring tube, the measuring tube must be made of non-magnetic, low electrical conductivity, low thermal conductivity and a certain mechanical strength material. Optional non-magnetic stainless steel, glass fiber reinforced plastic, high-strength plastic, aluminum, etc.
Electrode: Its function is to draw an induced potential signal proportional to the measured value. Electrodes are usually made of non-magnetic stainless steel and are required to be flush with the lining so as not to obstruct the flow. Its installation position should be perpendicular to the pipeline to prevent it from being deposited on it and affecting the measurement accuracy
Shell: Made of ferromagnetic material, it is the outer cover of the excitation coil of the power distribution system, which insulates the external magnetic field interference.
Lining: There is a complete electrical insulating lining on the inside of the measuring pipe and the sealing surface of the flange. It is in direct contact with the liquid to be measured, and its function is to improve the corrosion resistance of the measuring tube and prevent the induced potential from being short-circuited by the metal measuring tube wall. The lining materials are mostly corrosion-resistant, high-temperature, wear-resistant polytetrafluoroethylene plastics, ceramics, etc.
Converter: The induced potential signal generated by the liquid flow is very weak and is greatly affected by various interference factors. The function of the converter is to amplify and convert the induced potential signal into a unified standard signal and suppress the main interference signal. Its task is to amplify and convert the induced potential signal ex detected by the electrode into a unified standard DC signal

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