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1. Working principle of electromagnetic flowmeter
Working principle of electromagnetic flowmeter Electromagnetic flowmeters (EMF) are instruments made according to Faradays law of electromagnetic induction, used to measure the volumetric flow rate of conductive liquids. The working principle can be explained in detail as follows:
1. Measurement principle According to Faradays law of electromagnetic induction, when a conductor moves in a magnetic field and cuts magnetic lines, an induced electric potential e is generated at both ends of the conductor. This principle also applies to the flow of conductive liquids in a magnetic field. In a uniform magnetic field with a magnetic induction intensity of B, a non-magnetic pipeline with an inner diameter of D is placed perpendicular to the direction of the magnetic field. When a conductive liquid flows in the pipeline at a flow velocity u, the conductive fluid cuts the magnetic field lines. At this point, by installing a pair of electrodes perpendicular to the diameter of the magnetic field on the cross-section of the pipeline, the generation of induced electromotive force e can be detected. The magnitude of the induced electromotive force e is proportional to the magnetic induction intensity B of the magnetic field, the inner diameter D of the pipeline, and the average flow velocity u of the fluid, that is, e=BD (assuming that the flow velocity distribution is axisymmetric). From this, a linear relationship can be obtained between the volumetric flow rate qv of the pipeline, the induced electromotive force e, and the inner diameter D of the measuring tube, that is, qv is proportional to e and also proportional to D, but inversely proportional to the magnetic in
2. Structure Composition The electromagnetic flow Hes gauge consists of two parts: an electromagnetic flow sensor and a converter.
. Sensors are installed on industrial process pipelines, responsible for linearly transforming the volume flow rate of liquid flowing into the pipeline into an induced potential signal, and sending this signal to the converter through transmission lines. The converter is installed not too far from the sensor, which amplifies the flow signal sent by the sensor and converts it into a standard electrical signal output proportional to the flow signal for display, accumulation, and adjustment control.Thirdly, the excitation method, which generates a magnetic field, has a significant impact on the measurement accuracy and stability of electromagnetic flowmeters.
. There are currently three main excitation methods: Nuclear Kai DC excitation: DC excitation can generate a constant and uniform magnetic field, which is minimally affected by AC electromagnetic field interference. However, using a direct current magnetic field can easily polarize the electrolyte liquid passing through the measurement pipeline, generating positive and negative ions, causing the electrode to be surrounded by ions of opposite polarity, which affects the normal operation of the electromagnetic flowmeter. Therefore, DC excitation is generally only used for measuring non electrolyte liquids, such as liquid metals. AC excitation: The AC excitation method uses sine alternating current to generate an alternating magnetic field, which can eliminate polarization in