Electromagnetic flowmeters, also called magmeters, measure volumetric flow of conductive liquids in closed pipes using Faraday's law of induction, and the buyer-relevant spec gates are liner material, electrode alloy, minimum fluid conductivity, accuracy class, line size, and output protocol [S2][S4].
Standard offerings now cover DN15 through DN3000 with ±0.5% or ±1.0% of measured value accuracy, 4-20 mA plus HART or RS485 Modbus output, and IP68 submersible ratings for sizes up to DN1200 [S4].
Liner Material Selection by Fluid Chemistry
PTFE and PFA liners handle corrosive acids, caustics, and high-purity water, while hard rubber (NR) and polyurethane (PU) suit abrasive slurries, raw water, and sewage at lower cost [S4].
Endress+Hauser categorises its electromagnetic portfolio as Fundamental, Lean, and Extended selection, with the FLEX concept letting the same electronics platform adapt from basic water duty to demanding chemical and hygienic applications without re-engineering the transmitter [S1]. The practical read: a single plant can standardise on one vendor's electronics while still matching the liner to each service line.
Electrode Alloy and Conductivity Floor
Minimum fluid conductivity is 5 µS/cm for mains-powered units and 20 µS/cm for battery-powered remote units, so deionised water, high-purity rinse water, and many hydrocarbons fall outside the technology envelope and force a different choice such as a Coriolis flowmeter [S4]. A lined pipeline is also required, because electromagnetic flowmeters need a non-conductive bore to confine the induced voltage across the electrodes [S2].
Accuracy, Repeatability, and Size Range
Reference accuracy classes on commercial magmeters are ±0.5% and ±1.0% of measured value, with repeatability commonly specified at one-third of the accuracy figure, so a ±0.5% meter typically shows ≤ ±0.17% repeatability [S4].
Operating temperature and pressure are bounded by the liner: PTFE to roughly 180 °C, PFA to 200 °C, hard rubber below 80 °C, polyurethane below 70 °C, with PN10 to PN40 flange classes common [S3][S4]. Line size is the dominant cost driver, and a turbine flowmeter is often cheaper below DN50 while a magmeter wins on low pressure loss and no-moving-parts reliability above DN100.
Output Protocols and Process Integration
Standard outputs on current-generation magmeters are 4-20 mA analog, frequency or pulse (1-5000 Hz), and a digital channel that is either HART, RS485 Modbus RTU, or PROFIBUS PA depending on option code [S4][S6].
Diagnostic features worth pricing in are empty-pipe detection, excitation failure alarm, and bidirectional flow measurement, all standard on smart units and useful for custody and chemical-dosing services [S4].
Installation Geometry and Upstream Straight Run
Electromagnetic flowmeters require a full pipe for valid measurement, so they are unsuitable for partially filled gravity lines and for free-flowing open channels where a flow meter with a level-compensated primary is the correct choice [S2][S5].
Reference upstream straight-pipe requirements are 5 diameters and downstream 2 diameters for a typical single-elbow installation, materially shorter than vortex, orifice, or turbine primaries [S4]. Grounding rings or grounding electrodes are required when the adjacent pipework is lined, non-conductive, or internally coated, and skipping them is the most common field-installation cause of zero-shift errors and unstable readings.
Use Cases, Limitations, and Variants Comparison
Mainstream use cases are municipal water and sewage, chemical dosing, pulp and paper stock, food and beverage hygienic lines, mining slurries, and irrigation, all of which carry conductive liquids at flows where pressure loss matters [S2][S5][S6].
The technology is not suitable for hydrocarbons, oils, deionised water below the conductivity floor, or steam; buyers in those services should consider ultrasonic flowmeter clamp-on units for clean liquids or Coriolis for mass and density measurement.
Comparison across the main magmeter variants for selection: (1) flanged PTFE / 316L, suited to chemical and pharmaceutical duty at -40 to 180 °C with ±0.5% accuracy, the highest cost option; (2) wafer PTFE / Hastelloy, compact face-to-face for skid builders, similar accuracy, lower install cost; (3) flanged rubber or PU / 316L, suited to water, sewage, and slurry at lower cost with ±1.0% accuracy, limited to 70-80 °C; (4) battery-powered insertion magmeter, suited to remote district metering and irrigation at 20 µS/cm minimum conductivity, multi-year battery life but no continuous analog output [S4].
Buyer Checklist and Sourcing Signal
Shortlist logic: specify the fluid chemistry and conductivity first, then pick the liner-electrode pair, then set the accuracy class, then the output protocol, then the size and flange class; the reverse order is the most common cause of over-specified bids and the main reason an electromagnetic flowmeter ends up replaced within 18 months [S2][S4].
Trackable signals: the Endress+Hauser FLEX product family is the current reference for modular electronics spanning Fundamental, Lean, and Extended duty at the time of writing, and supply availability across DN1200 and larger sizes remains the dominant lead-time variable for municipal projects [S1]. For a broader vendor shortlist across flow technologies, see the spec-driven flow meter supplier map for 2026.