What are the reasons for the large fluctuations in electromagnetic flow meters?

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1. Working principle and scope of application of electromagnetic flowmeter

Electromagnetic flowmeter is a flowmeter that measures flow based on Faradays law of electromagnetic induction. The advantages of electromagnetic flowmeter are minimal pressure loss and a wide range of measurable flow rates. The ratio of high flow rate to low flow rate is generally above 20:1, suitable for a wide range of industrial pipe diameters, up to 3m after the stove is disassembled. The output signal is linear with the measured flow rate, with high accuracy. It can measure the fluid flow rate of acids, alkalis, salt solutions, water, sewage, corrosive liquids, as well as mud, slurry, pulp, etc. with conductivity ≥ 5 μ s/cm. But it cannot measure the flow of gas, steam, and purified water. When a conductor cuts magnetic field lines in a magnetic field, an induced potential is generated in the conductor, and the magnitude of the induced potential is proportional to the effective length of the conductor in the magnetic field and the speed at which the conductor moves perpendicular to the direction of the magnetic field. Similarly, when a conductive fluid flows vertically in a magnetic field and cuts magnetic induction lines, it will also generate induced potentials on the electrodes on both sides of the pipeline. The direction of the induced potential is determined by the right-hand rule, and the magnitude of the induced potential is determined by the following equation: Ex=BDv -- -- -- -- -- -- -- -- -- Equation

(1). In the formula, Ex - induced potential, V; B - magnetic induction intensity, TD - inner diameter of the pipeline, mv - average flow velocity of the liquid, m/s。 However, the volumetric flow rate qv is equal to th

(1) into this equation yields: Qv=(π D/4B) * Ex - - - - - - - Equation

(2). As can be seen from the above equation, 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. If an electrode is inserted on each side of the pipeline, an induced potential Ex can be introduced, and the magnitude of this potential can be measured to obtain the volumetric flow rate. According to Faradays principle of electromagnetic induction, a pair of detection electrodes are installed on the tube wall perpendicular to the axis of the measuring tube and the magnetic field lines. When the conductive liquid moves along the axis of the measuring tube, it cuts the magnetic field lines and generates an induced potential. This induced potential is detected by the two detection electrodes, and its value is proportional to the flow rate. Its value is E=BVDK, where E - induced potential; K - coefficient related to magnetic field distribution and axial length; B - Magnetic induction intensity; V - average flow velocity of conductive liquid; D - electrode spacing; (Measure the inner diameter of the tube). The sensor uses the induced potential E as a flow signal, which is transmitted to the converter. After signal processing such as amplification, transformation, and filtering, the instantaneous and cumulative flow rates are displayed on a backlit dot matrix liquid crystal display. The converter has 4-20mA output, alarm output and frequency output, and is equipped with communication interfaces such as RS-485, and supports

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