Flow Measurement · Glossary

What is an Electromagnetic Flow Meter?

Symbol: Magmeterconductive liquidsFlow Measurement

An electromagnetic flow meter measures the velocity of conductive liquids from the voltage induced as they flow through a magnetic field.

Electromagnetic Flow Meter Explained

By Faraday's law, a conductor moving through a magnetic field generates a voltage. The liquid is the conductor; electrodes pick up a voltage proportional to average velocity.

Magmeters are full bore with no pressure loss and no moving parts. The liquid must be conductive, and the pipe must run full. Grounding rings or electrodes are needed in plastic or lined pipes.

Electromagnetic Flow Meter Formula

E = k × B × D × v

E	induced voltage
k	meter constant
B	magnetic flux density
D	electrode spacing (pipe bore)
v	average velocity

Electromagnetic Flow Meter: Typical Values

Minimum conductivity (typical)	about 5 µS/cm, lower for some designs
Recommended velocity (typical)	about 1 to 3 m/s

Calculators for Electromagnetic Flow Meter

CalculatorMagnetic Flow Meter Sizing CalculatorFree online calculator with formula and worked example.CalculatorPipe Flow Velocity CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is an Electromagnetic Flow Meter?

An electromagnetic flow meter measures the velocity of conductive liquids from the voltage induced as they flow through a magnetic field.

Can a magmeter measure oil or demineralised water?

Oil, no. Very pure water is often below the minimum conductivity of standard meters; check the maker data.

Why does a magmeter read wrong in a partly full pipe?

It assumes the whole bore is full. Air at the top changes the flow area, so readings are wrong.

Learn more on the blog

Types of flow meters

A practical guide on instrumentationblog.in with more detail on electromagnetic flow meter and how it is applied on real plants.

Read Full Article

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