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How Electromagnetic Flow Meter Works?

Electromagnetic Flow Meters are based on FARADAY'S LAW INDUCTION. These meters are also called as Magflow or Electromagnetic Flow Meters. 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 at work is electromagnetic induction and mathematically defined as E=k*B*D*V.

where, E=Induced Voltage (Linear with velocity), k=Proportionality Constant, B=Magnetic Field Strength (Coil Inductance), D=Distance between electrodes, V=Velocity of process fluids.


Electromagnetic-Flow-Meters-Working-Principle

The induced voltage (E) is directly proportional to the velocity (V) of the fluid moving through the magnetic field (B). The induced voltage is carried to the transmitter through the electrode circuit. The transmitter then converts this voltage into a quantifiable flow velocity. The volumetric flow rate of the fluid is calculated using this known velocity along with the area of the pipe.

When a flowmeter is installed and activated, its operations begin with a pair of charged magnetic coils. As energy passes through the coils, they produce a magnetic field that remains perpendicular to both the conductive fluid being measured and the axis of the electrodes taking measurements. The fluid moves along the longitudinal axis of the flowmeter, making any generated induced voltage perpendicular to the field and the fluid velocity. An increase in the flow rate of the conductive fluid will create a proportionate increase the voltage level.

The meter features flanged construction and is available with choice of liner and electrode material. All meters consist of a sensor and a converter that may be mounted integral to the sensor or remotely either with a field mount kit.

Industrial Applications :

The Electromagnetic flow meter does not leave any obstructions in the pipe, so they are able to accommodate various applications from clean and conductive liquids. Electromagnetic flow meters are very well recommended for food grade applications like Juices, Milk, Municipal or Industrial Water etc. These meters are also suitable for liquids were there are lot of suspended particles like Sewage, Waste Water, Chemicals, Slurries etc.


Advantages of Electromagnetic Flow Meters Disadvantages of Electromagnetic Flow Meters Limitations of Electromagnetic Flow Meters

(1) The obstruction to the flow is almost nil and therefore this type of meters can be used for measuring heavy suspensions, including mud, sewage and wood pulp.

(2) There is no pressure head loss in this type of flow meter other than that of the length of straight pipe which the meter occupies.

(3) They are not very much affected by upstream flow disturbances.

(4) They are practically unaffected by variation in density, viscosity, pressure and temperature.

(5) Electric power requirements can be low (15 or 20 W), particularly with pulsed DC types.

(6) These meters can be used as bidirectional meters.

(7) The meters are suitable for most acids, bases, water and aqueous solutions because the lining materials selected are not only good electrical insulators but also are corrosion resistant.

(8) The meters are widely used for slurry services not only because they are obstruction less but also because some of the liners such as polyurethane, neoprene and rubber have good abrasion or erosion resistance.

(9) They are capable of handling extremely low flows.

(1) These meters can be used only for fluids which have reasonable electrical conductivity.

(2) Accuracy is only in the range of ± 1% over a flow rate range of 5%.

(3) The size and cost of the field coils and circuitry do not increase in proportion to their size of pipe bore. Consequently small size meters are bulky and expensive.

(1) The substance being measured must be conductive. Therefore, it can’t be employed for metering the flow rate of gases and steam, petroleum products and similar liquids having very low conductivity.

(2) To render the meter insensitive to variations in the resistance of liquid, the effective resistance of the liquid between the electrodes should not exceed 1% of the impedance of the external circuit.

(3) It is a very expensive device.

(4) As the meter always measures the volume rate, the volume of any suspended matter in the liquid will be included.

(5) To avoid any trouble which would be caused by entrained air, when the flow tube is installed in a horizontal pipe-line, the electrodes should be on the horizontal diameter.

(6) As a zero check on the installation can be performed only by stopping the flow, isolating valves are required and a bypass may also be necessary through which the flow may be directed during a zero check.

(7) The pipe must run full, in case regulating valves are installed upstream of the meter.

Related Products :



Electromagnetic Flow Meter -
ELMAG™ - 200


Electromagnetic Flow Meter -
ELMAG™ - 2516


Electromagnetic Flow Meter -
ELMAG™ - 2516LW


Battery Powered Electromagnetic Flow Meter - ELMAG™ - 600


Two Wire Electromagnetic Flow Meter - ELMAG™ TX-22

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