Electromagnetic flowmeters (EMF)

Although the measurement principle has been known since 1830, the first industrial electromagnetic flowmeters didn't appear in Holland until the 1950s.

Since then, this technology has gone from strength to strength, benefiting from new scientific and technical knowledge. For example, new materials have enabled the sensor to extend its field of application. Today, it is without doubt the best-selling flowmeter. It's also the easiest to use and the cheapest on the market, if we consider the quality/price ratio.

Despite its 60 years, this technology has lost none of its dynamism. Almost every year, a new advance is available on the market. The latest is the launch of stand-alone DWS, i.e. without an external power supply. They are fitted with batteries that give them a range of 3 to 15 years, depending on the manufacturer (see 7.6 ).

Of course, such innovations are only possible thanks to the dynamism of the world's four or five major automakers, who have invested heavily in research and development.

In France, we often use the term "DEM" to refer to electromagnetic flowmeters (MID in Germany).

The advantages of DEMs are manifold:

• Electromagnetic flowmeters do not interfere with fluid flow, so there are no pressure losses in the system, they have a linear response, with a wide range of pipe diameters (from a few 2 mm to 3000 mm), and are capable of measuring bidirectional flow. The right choice of electrodes and liner materials means they can be used for a wide variety of aggressive and corrosive liquids. They are particularly suitable for measuring slurries containing suspended particles, and are also widely used in paper production, the food industry, the chemical industry and water treatment.

• Electromagnetic flowmeters are relatively insensitive to the density and viscosity of the fluid to be measured, as well as to flow profiles; their main drawback is that they can only be used for conductive liquids (minimum 0.05 µS · cm ^-1 ).

• They have low installation requirements. Typical requirements are five times the nominal diameter (DN) in straight length upstream, and three times the same...