A magnetic flow meter (mag flow meter) is a volumetric flow meter which does not have any moving parts and is ideal for wastewater applications or any dirty liquid which is conductive or water based.
Magnetic flow meters will generally not work with hydrocarbons, distilled water and many non-aqueous solutions).
Magnetic flow meters are also ideal for applications where low pressure drop and low maintenance are required.
The operation of a magnetic flow meter or mag meter is based upon Faraday’s Law, which states that the voltage induced across any conductor as it moves at right angles through a magnetic field is proportional to the velocity of that conductor.
E is proportional to V x B x D where:
E = The voltage generated in a conductor V = The velocity of the conductor B = The magnetic field strength D = The length of the conductor
To apply this principle to flow measurement with a magnetic flow meter, it is necessary first to state that the fluid being measured must be electrically conductive for the Faraday principle to apply. As applied to the design of magnetic flow meters, Faraday’s Law indicates that signal voltage (E) is dependent on the average liquid velocity (V) the magnetic field strength (B) and the length of the conductor (D) (which in this instance is the distance between the electrodes).In the case of wafer-style magnetic flow meters, a magnetic field is established throughout the entire cross-section of the flow tube (Below Figure ).
If this magnetic field is considered as the measuring element of the magnetic flow meter, it can be seen that the measuring element is exposed to the hydraulic conditions throughout the entire cross-section of the flow meter. With insertion-style flow meters, the magnetic field radiates outward from the inserted probe .