Magnetic flow meter and Flow measurement

A mag meter (mag meter) is a sensor that measures fluid flow by the voltage induced across the liquid when the liquid flows through a magnetic field.A magnetic field is applied to the metering tube, which results in a potential difference proportional to the flow velocity perpendicular to the flux lines.The physical principle of operation is electromagnetic induction.Magnetic flowmeters require a conductive fluid, such as ionized water, and an electrically insulating pipe surface, such as rubber-lined steel pipe.If the direction of the magnetic field is constant, electrochemical and other effects at the electrodes can make the potential difference difficult to distinguish from that caused by fluid flow.To show this in modern magnetic flowmeters, the magnetic field is continuously reversed, canceling out the electrochemical potential difference that does not change direction with the magnetic field.However, this prevents the use of permanent magnets for magnetic flowmeters.

Flow measurement 

Flow measurement is the quantification of bulk fluid motion.Flow can be measured in various ways using a device called a flow meter. Common flow meter types with industrial applications are as follows:

• Obstruction type (differential pressure or variable area)

• Reasoning (Turbo).

• Electromagnetic.

• Positive displacement flow meters, which accumulate a fixed volume of fluid and then count the number of times the volume is filled to measure flow.

• Hydrodynamics (vortex shedding).

• Anemometer.

• Ultrasonic flow meter.

• Mass flow meter (Coriolis force).

Flow measurement methods other than positive displacement flow meters rely on indirect calculations of flow by the force exerted by a flowing stream of water overcoming a known constriction.Flow can be measured by measuring fluid velocity over a known area.For very large flows, flow can be inferred from changes in the concentration of dyes or radioisotopes using tracer methods.