Inductive flowmeters | Magnetic flowmeters | Mag tubes
Magnetic flowmeters, often referred to as MAG tubes, utilise Faraday's law to measure flow in conductive liquids. These flowmeters are particularly suited to applications in water and wastewater treatment, food production and the chemical industry, where they deliver high accuracy and reliability. MAG tubes are ideal for processes that require minimal maintenance and offer a long service life even in demanding environments.
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What is an inductive flowmeter (electromagnetic flowmeter)?
An inductive flowmeter - often called an electromagnetic flowmeter - is an instrument used to measure the volumetric flow of electrically conductive liquids in a pipe. It is based on Faraday's law of induction and is particularly useful in applications where other measurement techniques have difficulty performing, such as dirty, viscous or aggressive fluids.
Magnetic flow measurement vs inductive flowmeters - what is the difference?
In practice there is no technical difference - they are two different names for the same measurement technique.
- "Magnetic flux measurement" is a general term referring to the principle of using a magnetic field to measure the flow of a conductive fluid.
- "Inductive flow meter" or "electromagnetic flowmeter" is the name of the actual measuring instrument that uses this principle.
Both are based on Faraday's law of induction, where a voltage is induced in a conductive fluid as it moves through a magnetic field. This voltage is measured and converted into a precise flow value.
Summary:
Term |
What it means |
Magnetic flux measurement |
The actual principle of how the measurement is done |
Inductive flow meter |
The instrument that uses the principle to measure |
How does an inductive flowmeter (electromagnetic flowmeter) work?
An inductive flowmeter works by creating a magnetic field perpendicular to the fluid flow. When a conductive fluid passes through this magnetic field, a voltage (an electrical signal) is induced that is proportional to the flow rate of the fluid. Electrodes placed in the walls of the pipe record this voltage, and the instrument then calculates the volumetric flow rate based on known parameters such as the cross-sectional area of the pipe and the velocity of the fluid.
What distinguishes magnetic flux measurement from other measurement techniques?
What distinguishes magnetic flowmeters is:
- Requirements for electrically conductive liquids: They only work with liquids that have a certain conductivity (e.g. water with salts, acids, sludge). They are not suitable for non-conductive liquids such as oil or distilled water.
- No moving parts: Unlike turbine meters or vane meters, for example, inductive flowmeters have no mechanical parts that wear out, minimising maintenance.
- High accuracy and repeatability: They are highly accurate even at varying flow rates or with particle-contaminated fluids.
- Not dependent on flow profile: They are less affected by turbulence and pressure variations compared to e.g. differential pressure gauges.
