What is the measurement principle of electromagnetic flowmeter？

Case introduction

Faraday's Law of Electromagnetic Induction

The measurement principle of the electromagnetic flowmeter is based on Faraday's Law of Electromagnetic Induction. It consists of a non-magnetic alloy short tube lined with insulating material. Two electrodes penetrate the tube wall along the tube diameter and are fixed on the measuring tube. The electrode head is basically flush with the inner surface of the lining. When the excitation coil is excited by a bidirectional square wave pulse, an operating magnetic field with a magnetic flux density B will be generated in the direction perpendicular to the axis of the measuring tube. At this time, if a fluid with a certain conductivity flows through the measuring tube, it will cut the magnetic field lines and induce an electromotive force E. This electromotive force E is proportional to the product of the magnetic flux density B, the inner diameter d of the measuring tube and the average flow velocity V. The electromotive force E (flow signal) is detected by the electrode and sent to the converter through the cable. After the converter amplifies the flow signal, it can display the fluid flow and output pulses, analog current and other signals for flow control and regulation.

The working principle of the electromagnetic flowmeter is based on Faraday's law of electromagnetic induction:

When the conductive liquid moves in the magnetic field and cuts the magnetic field lines, the two ends of the conductor generate a wave that is perpendicular to the direction of movement and the direction of the magnetic field. The induced electromotive force E is proportional to the flow rate V of the conductive liquid, that is, E = BLV (B is the magnetic induction intensity, L is the length of the conductor, and V is the speed of cutting the magnetic lines of force).

After the converter is powered on, the excitation current drives the coil to form a magnetic field in the measuring tube. When the medium flows along the measuring tube and cuts the magnetic lines of force, the induced electromotive force generated is transmitted to the measuring tube through the two electrodes on the inner wall of the measuring tube. The converter performs signal processing and calculation to obtain the measured flow value.

The measured flow data is displayed on the display screen and output in the form of 4~20mA, pulse or fieldbus (RS485).