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Electromagnetic Meters and Magmeters: Industrial Grade Flow Sensors for Conductive Liquids

Quick Answer: Electromagnetic flow meters, also called magmeters, measure conductive liquids with no moving parts. They work on water, wastewater, chemicals, food slurries, and mining tails from DN15 up to DN2000. Silver Instruments supplies industrial grade magmeters with 4-20 mA HART, pulse output, PTFE or rubber liners, and ATEX Zone 1 options for sites in Southeast Asia, Oceania, Latin America, Africa, and the Middle East.

What a Magmeter Does in the Field

A magmeter measures flow by applying a magnetic field to the liquid. The conductive liquid passes through the field and generates a small voltage. Electrodes sense that voltage. The voltage is linear with flow velocity. Because the meter has no moving parts, it survives sand, sludge, and corrosive chemicals better than turbine meters.

In practice, most engineers pick a magmeter when the liquid conductivity is above 5 µS/cm. Standard magmeters cover clean water, wastewater, acids, caustic, brine, pulp stock, and many food products. They do not cover diesel, oil, or deionized water with very low conductivity. So check the conductivity before you quote a project.

Parameters That Decide Your Model and Quote

Pipe size drives the first decision. Standard sizes start at DN15 and go up to DN2000. A DN15 meter fits chemical dosing skids. A DN800 meter fits large desalination intake lines. For smaller lines under DN25, a compact display keeps the installation simple. For larger lines, remote mount electronics are easier to read at ground level.

Pressure and temperature set the liner choice. Rubber liners work up to 80°C and 10 bar in water and wastewater. PTFE liners handle aggressive acids and caustic up to 150°C. Polyurethane liners resist abrasive slurry. If the line runs at 16 bar, specify the pressure rating on the flange. Do not assume a standard PN10 body fits a PN16 system.

Electrode material depends on the chemical. 316L stainless steel covers water, low concentration acids, and most food liquids. Hastelloy C works for strong acids and seawater. Titanium works for brine and some chlorinated streams. Tantalum works for concentrated acids but costs more. We have seen customers in chemical plants try 316L first, then switch to Hastelloy C after a few months of pitting.

Output signals matter for the control room. Most Silver Instruments magmeters come with 4-20 mA HART, pulse, and RS485 Modbus RTU. A 4-20 mA HART signal gives flow rate and diagnostic data. Pulse output suits batching and totalizing. Modbus RTU fits PLC and SCADA systems. Always confirm the signal type with your integrator before the order.

Where These Meters Work Well

We sold a DN400 meter to a desalination plant in Vietnam. The intake seawater had conductivity around 48000 µS/cm. The pipe pressure was 6 bar and the temperature was 32°C. The line used a rubber liner and titanium electrodes. The plant needed 4-20 mA HART plus a local totalizer. The meter has run two years without electrode fouling.

A palm oil wastewater project in Indonesia used a DN80 magmeter on a sludge return line. The liquid had oil, sand, and about 800 µS/cm conductivity. A PTFE liner with 316L electrodes worked well because the stream was not strongly acidic. The customer wired the pulse output to a batch controller for polymer dosing.

A copper mine in Chile put a DN150 magmeter on tailings slurry. The slurry was abrasive, so we supplied a polyurethane liner and Hastelloy C electrodes. Pressure rating was PN16. The meter measured 120 m³/h with an accuracy of 0.2 percent. This is a typical mining tailings application where a Coriolis meter would plug or wear quickly.

A cooling water loop in Saudi Arabia used a DN250 meter. Water temperature was 45°C and pressure was 7 ba