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User’s Guide 2018
SAFMAG Electromagnetic Flowmeter
Theory of Operation
The operation of an electromagnetic flowmeter is explained by reference to Faraday’s law of
electromagnetic induction. This law states that the voltage induced across an electrical
conductor, as it moves at right angles through an electromagnetic field, is directly proportional
to the velocity of that conductor through the field. Mathematically this statement is
represented as shown below:
E = constant x B L V
Where:
E
=
the induced voltage
B
=
the electromagnetic field strength
L
=
the length of the conductor in the field
V
=
the velocity of the conductor (average velocity of the medium)
The volumetric flow of a conducting liquid or slurry is derived as follows:
Let L =
D (the diameter of the meter)
Then, E =
constant x B D V
Volumetric flow Q = V A (where A is the Cross-sectional area of the pipe)
Combining the above equations it is seen that if field strength is held constant then
E =
KQ (where K is a constant), thus the
induced voltage is directly proportional to
the volumetric flowrate.
