Magnetic Flowmeter

A magnetic flowmeter applies a magnetic field across the pipe; a conductive liquid moving through the field generates a voltage proportional to its velocity, which is picked up by two electrodes in the pipe wall. There is nothing in the flow path, so there is no pressure loss, no wear and no dependence on density, viscosity or temperature. Any liquid with more than a few microsiemens of conductivity can be measured, including sludge, pulp and abrasive slurries.

Meters are available from ½" to 36" with threaded or flanged connections, for velocities up to 12 m/s, process pressures from full vacuum to 100 bar and temperatures from −50 to +125 °C. The liner isolates the fluid from the steel tube and is chosen for the medium: hard rubber and polyurethane for water and abrasive slurries, PTFE and PFA for chemicals and hygienic service. Electrodes follow the same logic: 316 stainless steel, Hastelloy, tantalum, platinum or tungsten carbide for abrasion.

Outputs are 4–20 mA HART, pulse, FOUNDATION Fieldbus, PROFIBUS, Ethernet or Modbus. Options include grounding rings, a flow conditioner for short straight runs, empty-pipe detection, automatic electrode cleaning and in-situ verification that documents meter health without removal.

Magnetic flowmeters dominate water and wastewater, and are widely used in chemical, power, food and beverage and pharmaceutical plants wherever the liquid conducts.