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Magnetic Flow Meter

Things to Consider Before Purchasing a Magnetic Flow Meter

A magnetic flow meter measures the velocity of conductive liquids flowing through pipes. Examples of conductive liquids are water, acids, slurries, and caustics. Magnetic flowmeters only measure liquids with a conductivity level higher than 5mS/cm. If the flowmeter detects low-conductivity liquids, it will shut down. Here are some things to consider before purchasing one.

Faraday’s law

The electromagnetic flow meter functions by applying the principle of Faraday’s law of induction to the fluid flowing through it. This law states that a change in magnetic flux causes an electromotive force, or voltage, to be induced in the conductor. The higher the change in magnetic flux, the greater the induced voltage. The induced voltage is proportional to the rate of change of magnetic flux with time.

The alternating magnetic field created by a magnetic flow meter induces a voltage. This voltage is detected by electrodes on the flow tube’s walls. If an external coil is used, it must be protected by a non-conductive liner to avoid signal shorting. Because the fluid is a conductor in a magnetic field, the higher the voltage, the higher the flow. The voltage signal is converted into the volume of the flow using the pipe width.

Operation principle

The basic mechanism of a magnetic flow meter is based on a conductive liquid flowing through a magnetic field. The flow of this liquid induces a small voltage that is proportional to its velocity. Two stainless steel electrodes within the metering pipe sense the voltage and feed it into an electronic circuit. The signal is then processed by the microprocessor and converted into volumetric flow. This meter cannot be used for non-conductive substances.

In the basic principle, an electromagnetic flow meter operates by using the fluid in a pipe to create a magnetic field. This magnetic field is perpendicular to the longitudinal axis of the pipe. The flow of fluid causes a change in the level of voltage, thereby indicating a change in flow rate. This voltage increases with the flow rate. The flow rate increases in proportion to the voltage.


Magnetic flow meter offer highly accurate flow readings in wastewater and water applications. Compared to ultrasonic meters, magmeters offer greater flexibility, increased reliability, and low lifetime costs. Magnetic flow meters come in different configurations, including full-bore installations, hot-tap installations, and full-profile insertions. For full-bore installations, magmeters require only one diameter pipe length. In retrofit projects, these meters have low life-cycle costs.

A magnetic flow meter is simple to install, with just two basic components: a sensor


The most common application for magnetic flow meters is liquid with suspended solids. These conductive fluids must be monitored to ensure safety. Magnetic flow meters can measure the flow of most liquids, including water, acids and bases, slurries, and industrial wastes. Their operation is based on Faraday’s law of electromagnetic induction, where C = 2.2 x 104. This type of meter is used in the following industrial applications:

Water and wastewater applications include custody, transfer, and support processes. Mineral processing and mining applications involve the treatment of heavy media streams, including slurry streams. Other industries that commonly use flowmeters include the food and beverage industry, chemical industry, and oil and gas. Flowmeters are also used in the pharmaceutical and metals and mining industries. To install one, it is necessary to fill the pipe with liquid to be measured. Bypass pipe is also recommended for easier installation and maintenance.



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