This post gives more about electromagnetic flow meters, mostly used in instrumentation or control and automation industries, and its operating principle based on Faraday’s Law details.
Electromagnetic Flow meters work on below principle:
The operating or working principle of electromagnetic flow meters is based upon below Faraday’s Law of electromagnetic induction,
“It states that a voltage will be induced in a conductor moving through a magnetic field.”
Faraday’s Law:
E=kBDV
Where,
E = Induced Voltage,
B = Strength of the magnetic field,
D = Conductor Width,
V = Velocity of the conductor.
The magnitude of the induced voltage E is directly proportional to the velocity of the conductor V, conductor width D, and the strength of the magnetic field B.
Magnetic field coils placed on opposite sides of the pipe generate a magnetic field. As the conductive process liquid moves through the field with average velocity V, electrodes sense the induced voltage.
The width of the conductor is represented by the distance between electrodes. An insulating liner prevents the signal from shorting to the pipe wall. The only variable in this application of Faraday’s law is, the velocity of the conductive liquid V because, field strength is controlled constant and electrode spacing is fixed.
Therefore, the output voltage E is directly proportional to liquid velocity, resulting in the linear output of a magnetic resulting in the linear output of a magnetic flow meter.
Electromagnetic Flow mater features:
・Unaffected by the temperature, pressure, density, or viscosity of the liquid.
・Able to detect liquids that include contaminants (solids, air bubbles)
・There is no pressure loss.
・No moving parts (improves reliability)
However, some of the cons are, it cannot detect gases and liquids without electrical conductivity and a short section of straight pipe is required.