Electromagnetic flow meter is one of the velocity type flowmeter. It is a kind of flow detection system which works on Faraday’s law of electromagnetic induction. This law states that “a voltage will be induced when a conductor moves through a magnetic field”.1
An electromagnetic flowmeter can work with almost all liquids and slurries, as long as the liquid being measured is electrically conductive. In this type of flowmeter, a flow tube is the primary element which is installed straightforwardly in the pipe.
Since an electromagnetic flowmeter is a kind of inductional instrument, the liquid here acts as the conductor while the magnetic field gets created by energizing coils outside the flow tube. Now as a result of Faraday’s law, a voltage will be produced, the amount of which is directly proportional to the flow rate. A voltmeter can be connected directly to the flow tube or can be positioned at a little distance to indicate the voltage reading. In general, an electromagnetic flowmeter is constructed of a non-magnetic pipe lined with an insulating material. A typical electromagnetic flowmeter is shown in figure below:
- Electromagnetic flowmeters can be employed to measure more or less all electrically conducting fluids, pastes, slurries, acids, lyes, juices and emulsions including fluids with a conductivity as low as 0.5µS/cm i.e. 0.5µmhos.
- These types of flowmeters provide tremendous long term stability and accuracy.
- In addition to measuring the flow of common conductive liquid, an electromagnetic flowmeter is proficient to measure the flow of volume of liquid-solid mixed fluid, high-viscosity fluid and salt, strong acid and strong alkali as well.
- Fluid flow measurement via electromagnetic flowmeters is not at all affected by temperature, density, pressure or viscosity effects.
- Earlier electromagnetic flow meter designs needed a minimum fluidic conductivity of 1-5 microsiemens per centimeter for their proper functioning. The improved designs have brought down this obligation a hundredfold to between 0.05 and 0.1.
Electromagnetic flowmeters offer following major advantages:
- They consist of no moving parts; hence there are no restrictions to the flow.
- They are competent enough to measure intricate and corrosive liquids and slurries.
- Moreover, they are capable of measuring forward as well as reverse flow with the same accuracy.
- Initial designs of electromagnetic flowmeters involved high power consumption and zero meter settings (i.e. no flow to initially set the meter to zero). However, advanced designs have eradicated all these problems. New Pulse-type excitation techniques have reduced power consumption to a great extent. Zero meter settings are also no longer mandatory.