Accurate measurement of high flow water bodies is a key step in achieving optimal allocation of water resources, leakage control, and cost accounting in urban water supply systems, large-scale industrial water use, agricultural irrigation, and water conservancy projects. Traditional mechanical water meters face problems such as low start-up sensitivity, high pressure loss, easy wear, and accuracy degradation in large-diameter (DN200 and above) applications. The large-diameter electromagnetic water meter, with its unobstructed flow structure, high precision, wide range, and intelligent characteristics, has become a device for measuring large flow in modern smart water systems and is known as the "flow center" in the water supply network.

1、 Working principle and technical foundation

The large-diameter electromagnetic water meter operates based on Faraday's law of electromagnetic induction. When conductive liquids (such as tap water, reclaimed water, seawater, etc.) flow in a magnetic field, an induced electromotive force proportional to the flow velocity is generated. The water meter is equipped with an excitation coil and one or more pairs of electrodes inside. When a constant or alternating magnetic field is generated by the current passing through the coil, the water flowing through the measuring tube cuts the magnetic field lines and generates a weak voltage signal between the electrodes. After amplification, filtering, and digital processing, the signal is converted into a flow value and output.

2、 Core structure and key technical features:

1. Measurement tube body: Made of stainless steel or plastic lined carbon steel, with smooth inner walls and no flow blocking components, the pressure loss is almost zero, suitable for full or partially full tube flow (supported by some models).

2. Excitation system: Adopting low-frequency square wave excitation or dual frequency excitation technology, effectively suppressing polarization interference and zero drift, and improving the accuracy of small flow measurement.

3. Electrode design: Commonly used materials include 316L stainless steel, Hastelloy, or tantalum, suitable for different water qualities; The electrode structure includes standard type, scraper type (self-cleaning), capacitive type (non-contact), etc., to prevent scaling or corrosion from affecting the signal.

4. Lining material: lined with high polymer materials such as polyurethane (PU), PTFE (polytetrafluoroethylene) or F46, ensuring corrosion resistance and wear resistance, suitable for complex media such as sewage and seawater.

5. Intelligent Converter: Integrated microprocessor, LCD display screen, data storage module, and multiple output interfaces, supporting:

Instantaneous flow rate, cumulative flow rate, flow velocity, and forward and reverse flow rate display;

4-20mA analog output, pulse output, RS485 communication (Modbus protocol);

Upload remote data to SCADA or smart water platform.

3、 Main technical advantages:

High measurement accuracy: The basic error can reach ± 0.5%~± 1.0%, far better than the ± 2%~± 5% of mechanical water meters;

Wide range ratio: up to 40:1 or even 100:1, capable of accurately measuring small flow rates (such as small leaks at night) and withstanding instantaneous large flow rates;

No pressure loss, no wear: The straight through structure does not change the flow field, reduces pumping energy consumption, and has no mechanical wear, with a lifespan of up to 10-15 years;

Bidirectional metering: capable of automatically identifying forward and reverse flow, suitable for monitoring backflow in pipeline networks;

Strong anti-interference ability: not affected by changes in water quality, water pressure, and temperature, suitable for water bodies with high turbidity, bubbles, or small particles;

Intelligent and remote management: Supports wireless communication such as NB IoT, LoRa, 4G, etc., enabling remote meter reading, real-time monitoring, abnormal alarm (such as air traffic control, backflow, blockage), and data tracing.

Large caliber electromagnetic water meters are not only measuring tools, but also the "data entry point" for smart water management. It provides scientific basis for urban water resource management with high precision, high reliability, and intelligent characteristics. In the context of the "dual carbon" goal and the construction of a water-saving society, large-diameter electromagnetic water meters will continue to play a core role in helping to achieve the refinement, intelligence, and sustainable management of water resources.