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Introduction to the basic principle of electromagnetic flowmeter

Electromagnetic flowmeters are widely used in industry and medicine because of their convenient installation and use, simple structure and operation, high measurement accuracy, and the measurement results are not affected by external physical parameters, alarm function and fault self-diagnosis. And other industries. An electromagnetic flowmeter is a meter that measures the volumetric flow of a conductive liquid and is made using Faraday's law of electromagnetic induction. Since the early 1950s, China has realized the industrial application of electromagnetic flowmeters. In recent years, the production of electromagnetic flowmeters in the world has been at an important position in the production of industrial flow meters. In general, an electromagnetic flowmeter consists of a flow sensor transmitter. The flow sensor converts the volumetric flow of conductive liquid flowing through the pipe into a linear electrical signal. The transmitter is composed of an excitation circuit, a signal filtering amplifier circuit, an A/D sampling circuit, a microprocessor circuit, a D/A circuit, a transmission circuit, and the like. The conversion principle is Faraday's law of electromagnetic induction, that is, the conductor passes through the magnetic field, cutting the electromagnetic wire, and generating an electromotive force. The magnetic field of the flow sensor is realized by excitation. Most flow sensors now use low frequency square wave excitation. In the electromagnetic flowmeter, the conductive medium in the measuring tube is equivalent to the conductive metal rod in the Faraday test, and the two electromagnetic coils at the upper and lower ends generate a constant magnetic field. When a conductive medium flows, an induced voltage is generated. The two electrodes inside the pipe measure the induced voltage generated. The measuring pipe is electromagnetically isolated from the fluid and the measuring electrode by a non-conductive inner liner such as rubber or Teflon.

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