Flow measurement is the
quantification of bulk
fluid movement. Flow
can be measured in a
variety of ways. It
accumulates a fixed
volume of fluid and then
count the number of
times the volume is filled
to measure flow.
A magnetic flow meter (mag-
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
flowmeters will generally not
work with hydrocarbons,
distilled water and many non-
aqueous solutions). Magnetic
flowmeters are also ideal for
applications where low pressure
drop and low maintenance are
The operation of a magnetic flowmeter 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
•This law states that
e= B l v
•In of electromagnetic
conductor is the liquid
flowing through the
e = B D v
In Magmeter magnetic field is generated using
Electromagnets.The magnetic field has to permeate the
process liquid through the tube wall, and for that
reason the measuring tube should not have
Electrodes are used over here to sense the EMF generated in the
The electrodes are in direct contact with the process liquid. Their
material needs to be adequately resistant to corrosion and must allow
good electrical contact with the process liquid.
The most commonly used electrode materials are stainless steel grades,
Cr-Ni alloys, platinum, tantalum, titanium zirconium.
The Basic components of Electromagnetic flow
meter(so called Magmeter) are-
Teflon lined flow tube.
Excitation coils(for generation of magnetic field).
•Power usage is relatively low, with electrical power requirements as low as 15 watts
for some models.
•They are mechanically obstructionless and can be equipped with abrasion-resistant
liners, making them effective for measuring slurries and other erosive fluids.
• Relatively small amounts of electrode metals are needed for magnetic flowmeters.
• They can measure both very low flows and very high volume flow rates, with a
minimum diameter of roughly 0.125 inches and a maximum volume of up to 10 cubic
• They can usually measure multidirectional flow, either upstream or downstream.
No Moving Parts
Very Wide Rangeability
Ideal For Slurries
Unobstructed Flow Path
No pressure drop
Flow rate independent of viscosity,
temperature, and density
Measure dirty liquids with solids
Physical Pressure and Temperature
Measure conductive fluids
From this study, the following conclusions can be drawn:
• The motion of many fluids, flowing through an
electromagnetic flow meter, is not affected
by the magnetic field.
• The reverse, i.e. charged particles affecting the
magnetic field by their motion, can be neglected also.
• Most electromagnetic flow meters will be able to
measure the exact mean flow rate.
• The weight function is non uniform. So local
disturbances in the velocity profile can be liable for