Electromagnetic flow meters, also known as magmeters, are a type of flow meter that use electromagnetic induction to measure the flow rate of a fluid. These flow meters are particularly useful for measuring the flow rate of conductive fluids, such as water, acids, and bases.
The basic principle behind electromagnetic flow meters is Faraday’s law of electromagnetic induction. When a conductive fluid flows through a magnetic field, an electromotive force (EMF) is generated across the fluid, which is proportional to the velocity of the fluid. The magnitude of the EMF can be measured by two electrodes, which are placed in contact with the fluid and perpendicular to the direction of flow. The voltage generated between the electrodes is proportional to the flow rate of the fluid.
Electromagnetic flow meters typically consist of a flow tube made of non-conductive material, such as plastic or ceramic, with two electrodes mounted in the flow tube. The flow tube is surrounded by a magnetic field generated by a coil, which is powered by an external power supply. The magnetic field can be either a constant magnetic field or a pulsed magnetic field, depending on the design of the flow meter.
Electromagnetic flow meters have several advantages, including high accuracy, reliability, and low maintenance requirements. They are also able to measure the flow rate of both conductive and non-conductive fluids, and are not affected by changes in fluid density, viscosity, or temperature. However, they do have some limitations, including the need for a conductive fluid and the potential for signal interference from other sources of electromagnetic radiation.
Magnetic flow meters
Magnetic flowmeters measure the velocity of conductive liquids in pipes, such as water, acids, caustic, and slurries. Magnetic flowmeters can measure properly when the electrical conductivity of the liquid is greater than approximately 5μS/cm. Be careful because using magnetic flowmeters on fluids with low conductivity, such as deionized water, boiler feed water, or hydrocarbons, can cause the flowmeter to turn off and measure zero flow.
This flowmeter does not obstruct flow, so it can be applied to clean, sanitary, dirty, corrosive and abrasive liquids. Magnetic flowmeters can be applied to the flow of liquids that are conductive, so hydrocarbons and gases cannot be measured with this technology due to their non-conductive nature and gaseous state, respectively.
Magnetic flowmeters do not require much upstream and downstream straight run so they can be installed in relatively short meter runs. Magnetic flowmeters typically require 3-5 diameters of upstream straight run and 0-3 diameters of downstream straight run measured from the plane of the magnetic flowmeter electrodes.