Electromagnetic flowmeter is a flow measurement instrument based on Faraday's law of electromagnetic induction, which is dedicated to volume flow monitoring of conductive fluids. Its core principle is that when a conductive fluid flows through a magnetic field, an induced electromotive force is generated, which is proportional to the average flow velocity of the fluid, detected by electrodes and converted into a standard signal output

‌1. Structure and working principle‌

‌Core components‌

‌Magnetic circuit system‌: Generates an alternating magnetic field (50Hz power frequency) to avoid electrode polarization caused by a DC magnetic field.

‌Measuring catheter‌: Use non-magnetic materials (such as stainless steel, ceramics) to ensure that magnetic lines of force penetrate the fluid.

‌Electrode‌: Non-magnetic stainless steel material, flush with the lining to prevent sediment accumulation.

‌Lining‌: Insulating material (such as polytetrafluoroethylene, rubber), corrosion-resistant and isolated potential short circuit.

‌Converter‌: Amplifies weak induction signals, suppresses interference, and outputs 4-20mA or digital signals.

‌2. Core features‌

‌No pressure loss‌: The pipeline has no obstruction parts, supports bidirectional measurement, and needs to ensure a straight pipe section (upstream ≥10D, downstream ≥5D).

‌Strong anti-interference‌: The measurement is not affected by changes in density, viscosity, pressure, and temperature‌.

‌Wide applicability‌: The pipe diameter covers DN3–DN3000, and is resistant to strong acid and alkali/particle-containing media, such as mud and sewage (through lining/electrode material adaptation).

️Key limitations:

‌Medium requirements‌: Only applicable to conductive liquids (conductivity ≥5μS/cm), gas/petroleum products cannot be measured‌.

‌Installation conditions‌: The full pipe state must be ensured, and the straight pipe section requirements are: upstream ≥5DN, downstream ≥2DN‌.

‌Environmental interference‌: Strong electromagnetic fields need to be shielded (<400A/m)

‌3. Typical application scenarios‌

Chemical industry: Strong acid and alkali flow monitoring (lining corrosion-resistant design).

Water treatment: Municipal sewage and industrial wastewater metering (anti-impurity interference).

Food and medicine: hygienic design to meet aseptic requirements.

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4, key parameters for selection ‌reference‌

. ‌Process parameters‌: medium adaptability, fluid properties (corrosiveness/cleanliness), temperature/pressure range (high pressure customization can reach 32MPa), flow range, ‌conductivity‌ ≥5μS/cm.

. ‌Structural form‌: ‌Integrated type‌: normal temperature and low pressure environment (≤180℃) ‌Split type‌: high temperature/harsh site (sensor temperature resistance, converter remote installation) ‌Plug-in type: suitable for large-diameter pipelines ‌

5, mainstream technology classification ‌ ‌Low-frequency excitation type‌: strong anti-interference, suitable for fluids containing impurities (such as slurry). ‌High-frequency excitation type‌: accuracy ±0.1%, suitable for clean liquids (such as pharmaceutical pure water). ‌Dual-frequency excitation type‌: adaptive to complex working conditions (such as bubble/particle mixed fluid).