Electromagnetic Water Flow Meter Working Principle

Email: sales01@cxflowmeter.com

WhatsApp: 008618049841995

Electromagnetic Water Flow Meter Working Principle

The operating principle of an electromagnetic water flow meter is based on Faraday's law of electromagnetic induction, which states that 

when a conductor moves in a magnetic field, an induced electromotive force (EMF) is generated that is proportional to the conductor's velocity

 and the strength of the magnetic field. The following is a detailed explanation of its core operating principle:

1. Magnetic Field Generation

Excitation Coil: The sensor portion of the electromagnetic water flow meter is equipped with an excitation coil. When energized, it generates 

a uniform magnetic field perpendicular to the pipe axis.

Magnetic Field Characteristics: The direction of the magnetic field is perpendicular to the direction of liquid flow, ensuring that the liquid cuts

 the magnetic flux lines.

2. Electromotive Force Induction

Conductive Liquid Flow: When a conductive liquid (such as water) flows through a magnetic field, the charged particles (ions) in the liquid 

are deflected by the Lorentz force, accumulating charge on electrodes on both sides of the pipe.

Induced Electromotive Force: An induced electromotive force (voltage) is generated between the electrodes. Its magnitude is proportional 

to the liquid flow rate and its direction is perpendicular to the magnetic field and flow direction (right-hand rule).

3. Signal Acquisition and Processing

Electrode Detection: Electrodes installed on both sides of the pipe wall directly contact the liquid to detect the induced EMF. Signal 

Transmission: The electrodes transmit weak electromotive force signals to the transmitter (converter).

Signal Processing: The transmitter amplifies, filters, and linearizes the signal to eliminate interference (such as power frequency noise

 and fluid electrochemical noise).

Flow Calculation: Flow rate is calculated according to the formula E=k⋅B⋅v⋅D

(or Q=A⋅v

), where:

E

is the induced electromotive force,

k

is the instrument constant,

B

is the magnetic flux density,

v

is the liquid flow rate,

D

is the pipe inner diameter,

Q

is the volume flow rate, and

A

is the pipe cross-sectional area.

4. Output and Display

Standard Signal Output: The transmitter converts the calculated result into a standard signal (such as 4-20mA, pulse, RS485, etc.) for display, 

recording, or control system use.

Bidirectional Measurement: Supports forward and reverse flow measurement, suitable for complex piping systems.

5. Structural Features

Measuring tube: Made of non-magnetic material (such as stainless steel), with an insulating lining (such as rubber or PTFE) to prevent short

 circuits and accommodate corrosive media.

No obstructing elements: No moving parts in the pipe, resulting in minimal pressure loss and long service life.

Anti-interference design: Low-frequency rectangular wave excitation reduces power frequency interference; the electrodes are flush with 

the lining to prevent sediment accumulation.

6. Application Advantages

High Precision and Stability: Measurement accuracy reaches ±0.5%, with minimal impact on fluid density, viscosity, temperature, and pressure.

Wide Turndown Ratio: With a turndown ratio of up to 100:1, it is suitable for measuring low to high flow rates.

High Adaptability: Suitable for measuring corrosive liquids and liquids containing solid particles (such as sewage and slurries), provided the

 liquid conductivity is ≥5 μS/cm.

Low Pressure Drop: No obstructing elements in the pipe, resulting in low energy consumption.

7. Installation Requirements

Full-pipe installation: Ensure the pipe is completely filled with liquid to prevent air accumulation and measurement errors. Straight pipe 

sections: A certain length of straight pipe is required (usually 5D in front and 3D in the back) to eliminate the effects of eddy currents.

Avoid interference: Keep away from strong electromagnetic field sources (such as high-power motors and inverters) to prevent signal

 interference.

For more information on electromagnetic flow meter selection and quotes, please contact: 

Email: sales01@cxflowmeter.com

WhatsApp: 008618049841995