The working principle of electromagnetic flowmeter is based on Faraday's law of electromagnetic induction. In an electromagnetic flowmeter, the conductive medium inside the measuring tube is equivalent to a conductive metal rod in Faraday's test, and the two electromagnetic coils at the upper and lower ends generate a constant magnetic field. When a conductive medium flows through, an induced voltage will be generated (the working principle is shown in the following figure). The induced voltage generated by measuring the two electrodes inside the pipeline. The measuring pipeline achieves electromagnetic isolation from the fluid and measuring electrodes through non-conductive lining (rubber, Teflon, etc.). The functions of electromagnetic flow meters on the market vary greatly, with some simply measuring one-way flow and only outputting analog signals to drive the rear instrument; Multi functional instruments include bidirectional flow measurement, range switching, upper and lower limit flow alarm, air traffic control and power cut-off alarm, small signal cut-off, flow display and total calculation, automatic verification and fault self diagnosis, communication with the upper computer, and motion configuration. The serial digital communication function of some models of instruments can be equipped with multiple communication interfaces and dedicated chips (ASICs) to connect to HART protocol systems, PROFTBUS, Modbus, FF fieldbus, etc. Electromagnetic flow meters have a series of excellent characteristics that can solve problems that are not easily applicable to other flow meters, such as measuring dirty and corrosive flows. In the 1970s and 1980s, there were significant technological breakthroughs in electromagnetic flux, and its applications were very extensive.
Advantages of electromagnetic flowmeter:
1: The measuring channel is a smooth straight pipe that will not block, suitable for measuring liquid-solid two-phase fluids containing solid particles, such as pulp, mud, sewage, etc
2: No pressure loss caused by flow detection, good energy-saving effect
3: The measured volumetric flow rate is actually not significantly affected by changes in fluid density, viscosity, temperature, pressure, and conductivity;
4: Large flow range and wide aperture range;
5: Can be used with corrosive fluids.
Disadvantages of electromagnetic flowmeter:
1: Cannot measure liquids with low conductivity, such as petroleum products
2: Cannot measure gases, vapors, and liquids containing large bubbles
3: Cannot be used for higher temperatures.
Electromagnetic flow meters have a wide range of applications, with large-diameter instruments being commonly used in water supply and drainage engineering; Small and medium-sized calibers are commonly used in high demand or difficult to measure applications, such as cooling water control for blast furnace tuyere in the steel industry, measurement of pulp and black liquor in the paper industry, strong corrosive liquids in the chemical industry, and slurry in the non-ferrous metallurgy industry; Small caliber and micro caliber are commonly used in places with hygiene requirements such as the pharmaceutical industry, food industry, and biochemistry.
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