Measuring principle of electromagnetic flowmeter - News - Global IC Trade Starts Here.

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According to Faraday's law of electromagnetic induction, when a conductor moves and cuts magnetic lines of force in a magnetic field, an induced potential e is generated at both ends of the conductor, the direction of which is determined by the right-hand rule, the magnitude and magnetic induction of the magnetic field B, and the conductor is within the magnetic field. The length L is proportional to the speed u of the conductor. If B, L, and u are perpendicular to each other, then

e=Blu(3-35)

Similarly, in a uniform magnetic field with a magnetic induction intensity of B, a non-magnetic tube with an inner diameter D is placed perpendicular to the direction of the magnetic field. When the conductive liquid flows at the flow velocity u in the tube, the conductive fluid cuts the magnetic field lines. If in the pipeline A pair of electrodes mounted on both ends of the diameter perpendicular to the magnetic field in the cross section can prove that as long as the flow velocity distribution in the pipe is axially symmetric, an induced electromotive force is also generated between the two electrodes:

e=BD(3-36)

Where is the average flow rate on the section of the pipe. The volumetric flow rate of the pipe is thus:

Qv=(3-37)

It can be seen from the above formula that the volume flow rate qv is linear with the induced electromotive force e and the inner diameter D of the measuring tube, and inversely proportional to the magnetic induction intensity B of the magnetic field, independent of other physical parameters. This is the measurement principle of the electromagnetic flowmeter.

It should be noted that in order for the formula (3-37) to be strictly established, the electromagnetic flowmeter measurement conditions must satisfy the following assumptions:

1 magnetic field is a uniformly distributed constant magnetic field;

2 the flow velocity of the measured fluid is axially symmetrically distributed;

3 The liquid to be tested is non-magnetic;

4 The conductivity of the liquid to be tested is uniform and isotropic.