Electromagnetic flowmeter(EMF), also known as magmeter/mag flowmeter, is a widely used instrument for measuring flow rate of electrically conductive liquid in industrial and municipal applications. The instrument can offer a reliable and non-intrusive volumetric flow measurement solution leveraging Faraday’s law, suitable for liquid medium with appropriate conductivity.
Its induced electromotive force E can be expressed by the following formula:
E=KBVD
Where
K= Flowmeter constant
B= Magnetic induction intensity
V= mean flow velocity in cross section of measuring pipe
D= Inner diameter of measuring pipe
Working Principle
The fundamental principle of operation for the mag flowmeter is Faraday’s law of electromagnetic induction. It states that when a conductor moves through a magnetic field, electromotive force would be induced.
Specially in the case of electromagnetic flowmeter’s operation, conductive liquid flowing through pipe of the instrument serves as the conductor. A pair of coils generates a uniform magnetic field perpendicular to the flow direction. The magnetic field lines would be cut through by flow. Induced electromotive force is therefore generated and subsequently sensed by a pair of metal electrodes and processed into standard electrical signal output.
Advantages of Magnetic Flow Measurement
Structural simplicity: EMF’s construction does not have any moving parts, whose absence reduces mechanical wear and maintenance need. There is also hardly any obstruction inside its measuring pipe that could lead to attrition of pressure head and clogging of viscous medium.
Less mounting requirements: Installation of EMF require relatively shorter length of up & downstream straight pipe sections. Operating independently, the mag flowmeter dost not require differential pressure transmitter to assist its measurement. Flow can be measured in both direction, reducing restriction for meter orientation and is suitable for applications of reverse flow monitoring.
Compatibility: Mag flow measurement can exhibit stable and reliable performance that hardly affected by physical medium parameters of pressure, temperature, density and viscosity. Customizable lining materials and electrode metals cab anti-corrosion and wear resistant demands, applicable for wide ranges of aggressive chemical, abrasive slurry, and sanitary requiring liquid media.
Accuracy: Electromagnetic approach features highly accurate measuring among various volumetric flow measuring methods. EMF accuracy is generally ±0.5% to ±0.2% of reading.
Limitations
Conductivity required: The measuring fluid of EMF is required to have sufficient conductivity(≥5μS/cm). Hence gas and non-conductive liquid are beyond the reach of electromagnetic flow measurement. Common industrial non-conductive media like steam purified water, organic solvents and oil products are not able to utilize this flow monitoring method.
Fully filled pipe: The operation of EMF requires full submersion and continuous contact of electrodes with conductive fluid. Therefore during measurement the process must ensure that pipe section of EMF is entirely filled with medium in order to achieve optimal performance.
Application
Based on its unique measurement principle, electromagnetic flowmeter is particularly well-suited for measurement of conductive liquids in scenarios such as:
Water Supply: Measuring inlet raw water and outlet treated water flow for water resource management.
Sewage Treatment: Measuring municipal sewage, industrial effluent, and sludge with adequate conductivity.
Chemical: Measuring various acids, alkali, salt solutions, and other highly corrosive media using corrosion-resistant linings and electrode materials.
Beverage: Measuring raw materials, intermediates and finished products during production of milk, juice, alcoholic drink and other beverages.
Metallurgy: Measuring mineral slurry, tailing slurry, coal slurry water in ore processing with wear-resistant materials.
Energy: Measuring circulating cooling water, condensate, chemical treatment fluids in power plant processes, etc.
Shanghai Wangyuan has over 20 years of experience manufacturing and servicing measurement instrumentation. Our extensive professional knowledge and case studies across fields with all kinds of flow meters enable us to provide flow monitoring solutions that meet your demands exactly. If there is any questions and needs about electromagnetic flow meters, please don't hesitate to reach out to us.
Post time: Jun-03-2025