Home » The working principle of magnetic flow meters and what are they?

The working principle of magnetic flow meters and what are they?

by Uneeb Khan

What is a Magnetic Flow Meter?

A magnetic flow meter is a mass or volumetric flow meter that uses electrodes connected to the liquid flow to measure the velocity of liquids in a tube or pipe. They can take readings without moving parts because of their unique design. Due to this particular feature, they are able to measure high pressure applications without fear of leakage or seepage.

The conductivity of fluid measured by magnetic flow meters is at or above three micro siemens. Faraday’s law is used to measure the voltage and velocity of fluids, which requires a certain level of conductivity for the voltage to be generated. It depends on the manufacturer what conductivity is required, but it is always between 3 and 10 micro Siemens, with some manufacturers having higher requirements.

Temperature, pressure, viscosity of liquids, and density of liquids do not affect the consistency and accuracy of magnetic flow meters. Greasy viscous materials are easily and efficiently measured.

Magmeters, electromagnetic meters and electromagnetic flow meters are all terms that engineers use interchangeably; however, Magmeters are the most common.

What is the working principle of magnetic flow meters?

A magnetic flow meter measures and calculates the flow of a conductive liquid by generating a magnetic field. As the speed of the flow increases, the voltage that it generates becomes greater and passes a signal to the meter. An electric flow meter measures how fast or how fast a conductive liquid or fluid flows and moves through a pipe or conduit.

As defined by Faraday’s Formula, the signal voltage (E) of a magnetic flow meter is proportionately constant (k) depending on the liquid velocity, magnetic field strength, and distance between electrodes. It is necessary to have an electrically conductive fluid to use this principle.

When a conductor moves at a 90° angle to a magnetic field, an electromagnetic field (EMF) is generated. If a conductor is placed in the magnetic field, an electric current is generated.

Magnetic Field Coils

Using rods, two field coils are positioned inside the magnetic flow meter, generating a magnetic field across the tube being measured. The electrical voltage is detected by electrodes placed right at the end of the tube or pipe. Between the conductive fluid and the metal body of the wall sensor, there is a lining placed as a protective measure and to prevent an electrical short circuit.

Flow Measurement

The electric charge particles are evenly distributed when the tube or pipe is empty, as there is no induced voltage between the electrodes. During flow, the magnetic coils separate the positively and negatively charged particles, collecting the negatively charged particles on one side of the pipe when the flow begins. Electrodes detect the electrical voltage produced by positively charged particles. A conductor’s flow rate determines the strength of the induced voltage.


In a magnetic flow meter, the voltage, strength of the magnetic field, and distance between the electrodes are used to calculate the flow rate of fluid in a pipe. Water, polymers, surfactants, and chemicals can be measured using the meter’s readings and data to determine the total flow rate.

By using the electrode circuit, the induced voltage is transmitted to the transmitter, which converts the data from the electrodes into a quantifiable flow rate. Based on the velocity and the area of the pipe, the volumetric flow rate can be calculated and displayed on the meter.

Parts of a Magnetic Flow Meter

One of the major advantages of magnetic flow meters is that they are simple to use. They are constructed of two basic parts, one of which connects to a pipe and one of which collects readings. The sensor is attached to the pipe and the transmitter is mounted on top of it, as shown in the diagram below.

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