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This post was last edited by hdyqyb on 2019-11-19 at 14:56. I. Principle of electromagnetic flowmeters Electromagnetic flowmeters are instruments that measure the volumetric flow rate of conductive liquids, and they are based on Faraday’s law of electromagnetic induction. In addition to measuring the volumetric flow rate of ordinary conductive liquids, sewage flow meters can also be used to measure the volumetric flow rate of highly corrosive liquids such as strong acids and strong bases, as well as uniform liquid-solid suspension fluids like sludge, pulp, and paper pulp. It is widely used for flow measurement in various industrial sectors such as petroleum, chemicals, metallurgy, light textiles, papermaking, environmental protection, and food processing, as well as in areas like municipal management, water conservancy construction, and river dredging. In an electromagnetic flowmeter, the conductive medium inside the measurement tube (the substance that plays a decisive role) is equivalent to the conductive metal rod in Faraday’s experiment; the two electromagnetic windings at the upper and lower ends generate a constant phenomenon: the radiation of waves and particles. When a conductive medium flows through, an induced voltage is generated; this voltage is proportional to the flow velocity of the fluid, thereby allowing the flow rate Q to be determined. II. Classification of Electromagnetic Flow Meters Electromagnetic flow meters are classified according to the method of excitation current: there are direct current excitation, alternating current (power frequency or other frequencies) excitation, low-frequency rectangular wave excitation, and dual-frequency rectangular wave excitation. Classified by the standard of output signal connection and excitation (or power supply) wiring, there are four-wire systems and two-wire systems. Classified by the installation method of the converter and sensor combination, there are separate-type and integrated-type. (Pressure transmitters) Classified by the way in which the flow sensor is connected to the pipeline, there are flange type, clamp type (clamp-type electromagnetic flowmeter), sanitary type (sanitary-type electromagnetic flowmeter), insertion type (insertion-type electromagnetic flowmeter), and threaded connection type (high-pressure electromagnetic flowmeter with threaded connections). Classified by whether the flow sensor electrodes come into contact with the liquid being measured, there are contact-type and non-contact-type types. Classified by sensor structure based on flow rate (unit: cubic meters per second), there are short-tube type and insertion type (insertion-type electromagnetic flowmeter). Vortex flow meters are also known as vortex meter or Karman vortex flow meter. These products are carefully designed by integrating advanced technologies from developed countries and drawing on years of experience in research and production; they feature intelligence, standardization, serialization, versatility, and the use of standardized manufacturing molds, all of which ensure the aesthetic quality of the products. Classified by application, there are general-purpose types, explosion-proof types, sanitary types, water-resistant types, and submersible types for measuring flow in open channels (open-channel flow meters). III. Requirements for the installation environment of electromagnetic flowmeters The protection rating of the housing of electromagnetic flowmeters is generally IP65 (according to the international standard GB4208 for housing protection ratings – dust and water resistance). The main requirements for the installation environment are as follows: (1) The sensor should be installed in a dry and well-ventilated area, away from places that are humid or prone to water accumulation; direct sunlight and rain exposure should also be avoided as much as possible. (2) Installation in areas with excessively high ambient temperatures should be avoided as much as possible. The electromagnetic flowmeter with an integrated structure (unit: cubic meters per second) is also subject to the ambient temperature of the electronic components, which should be kept low. (3) The pipes on which sensors are installed should not have high leakage currents, and they should be kept as far away as possible from devices with strong electrical properties, such as large electromechanical devices and large transformers, to avoid electromagnetic interference ； (4) The pipeline or floor on which the sensor is installed should not experience severe vibrations, especially in the case of integrated instruments ； (5) The location for installing sensors should take into account the space available for on-site maintenance by staff. The function of an electromagnetic flowmeter is to generate a uniform direct-current or alternating-current magnetic field. The DC magnetic circuit is implemented using permanent magnets, which have the advantage of a relatively simple structure and are less affected by alternating magnetic fields. However, they can cause polarization of the electrolyte fluid flowing through the measurement conduit, with positive ions surrounding the negative electrode and negative ions surrounding the positive electrode – that is, a polarization phenomenon of the electrodes. This leads to an increase in the internal resistance between the two electrodes, thereby severely affecting the proper operation of the instrument. For more information, please visit the company’s official website at http://www.yb1518.com/. Please retain this link when reproducing the content! http://www.yb1518.com/UploadFiles/2012717174126829.jpg