Electromagnetic Flowmeters

Electromagnetic Flowmeters

Electromagnetic flowmeters (magmeters) measure the volume flow of electrically conductive liquids using a non-intrusive sensing principle with no moving parts. They are applied to conductive services such as water, acids, alkalis, and slurries, and are commonly used for monitoring, filling, dosing, and custody-transfer measurement where stable, repeatable volume measurement is required.

The measuring principle follows Faraday’s law: a conductive liquid moving through a magnetic field induces a voltage. Field coils generate the magnetic field and electrodes pick up the induced voltage, which is proportional to flow velocity and therefore to volumetric flow. A pulsed DC field with alternating polarity helps stabilize the zero point and improves robustness in multiphase or inhomogeneous liquids and in low-conductivity conditions.

Key benefits include measurement that is largely independent of pressure, density, temperature, and viscosity, along with a full-bore, unobstructed pipe that avoids added pressure loss. The absence of moving parts makes the technology effectively maintenance-free, and the free cross-section supports CIP/SIP cleaning and pigging in appropriate designs. Magmeters also tolerate entrained solids, enabling accurate metering of challenging mixtures such as ore slurry or cellulose pulp.

Typical deployments span municipal and industrial water management, process industries, life sciences, and food and beverage services. In abrasive slurry applications - mining, tunneling, and bulk solids transport - robust magmeters are often selected where other technologies struggle with wear or profile disturbances.

Specification focuses on confirming minimum conductivity, selecting liner and electrode materials for corrosion and abrasion resistance, and ensuring proper grounding and installation to avoid noise and empty-pipe effects. Upstream/downstream hydraulic conditions still matter for stability (e.g., avoiding partially filled pipes or gas pockets), but straight-run requirements are typically modest compared to many inferential technologies. Integrating diagnostics and digital communications can further reduce lifecycle cost by simplifying verification and improving asset visibility.

George E. Booth Co., an exclusive authorized representative of sales and service for Endress+Hauser.