The principle of electromagnetic flowmeter

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1. Introduction to the working principle of electromagnetic flowmeter

The working principle of electromagnetic flowmeter Electromagnetic flowmeter is a flowmeter that measures flow according to Faradays law of electromagnetic induction. The working principle is briefly described as follows:

1. Basic principle: When a conductor cuts magnetic field lines in a magnetic field, an induced potential is generated in the conductor. Similarly, when a conductive fluid flows vertically in a magnetic field and cuts magnetic induction lines, induced potentials are also generated on the electrodes on both sides of the pipeline. The magnitude of induced potential is proportional to the effective length of the conductor in the magnetic field, the speed at which the conductor moves perpendicular to the magnetic field direction, and the intensity of magnetic induction.

Secondly, the relationship between induced potential and flow rate. The expression for induced potential Ex is: Ex=BDv, where Ex is the induced potential.

; B is the magnetic induction intensity; D is the inner diameter of the pipeline; V is the average flow velocity of the liquid. And the volumetric flow rate Qv is equal to the product of the fluid velocity v and the pipeline cross-sectional area (π D ²)/4. Substituting the expression for induced potential into the formula for volumetric flow rate yields Qv=(π D/4B) * Ex. It can be inferred that when the diameter D of the pipeline is fixed and the magnetic induction intensity B remains constant, the measured volume flow rate is linearly related to the induced potential. Thirdly, a pair of detection electrodes were installed on the pipe wall perpendicular to the axis of the measuring tube and the The principle of electromagnetic flowmeter

The principle of electromagnetic flowmeter

magnetic field lines during the measurement process. When the conductive liquid moves along the axis of the measuring tube, it cuts the magnetic field lines and generates an induced potential, which is detected by two detection electrodes. The magnitude of the induced potential is directly proportional to the flow velocity, with a value of E=B · V · D · K, where K is a coefficient related to the magnetic field distribution and axial excitation length. The sensor transmits the induced potential E as a flow signal to the converter. After the converter amplifies, transforms, filters, and processes the signal, it displays instantaneous and cumulative flow rates using a backlit dot matrix LCD display. The converter also has functions such as 4-20mA output, alarm output, and frequency output, and is equipped with communication interfaces such as RS-485, supporting HART and MODBUS protocols. 4. Characteristics and Applications: Measurement is not affected by changes in fluid density, viscosity, temperature, pressure, and conductivity: Since the measured potential is induced, it is not affected by these factors. There are no obstructing flow components or pressure loss inside the measuring tube: The electromagnetic flowmeter has no movable parts or flow blocking components, which will not cause pressure loss. Reasonably select sensor lining and electrode materials, with good corrosion resistance and wear resistance. Vertical socks are suitable for measuring various corrosive liquids and slurries. The converter adopts a new excitation method with low power consumption, stable zero point, and high accuracy: the flow range can reach 150:1. It can measure the volumetric flow rates of liquid-solid two-phase flow, high viscosity liqui

1. Introduction to the working principle of electromagnetic flowmeter

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