Shanghai YichuanSince the late 1950s, electromagnetic flowmeters have been widely used and developed in flow measurement in China. The working principle of an electromagnetic flowmeter is based on Faraday's law of electromagnetic induction, which states that the measured medium flows perpendicular to the direction of magnetic field lines, thus generating an induced electromotive force EX in a direction perpendicular to both the medium flow and magnetic field lines. When the magnetic field strength B and the distance d between the two poles are constant, the induced electromotive force EX is proportional to the flow rate (velocity) of the measured medium. Electromagnetic flow meters are not affected by external factors such as temperature, pressure, viscosity, and weight, and there is no pressure loss inside the measuring tube due to contraction or protrusion. In addition, the initial signal detected by the flow element is a voltage that varies precisely linearly with the average flow velocity of the fluid, and is independent of other properties of the fluid, thus possessing great flexibility. According to the characteristics of large flow rate changes, impurities, low corrosiveness, and certain conductivity of sewage, electromagnetic flowmeter is a good choice for measuring the flow rate of sewage. It has a compact structure, small volume, and is easy to install, operate, and maintain. If the measurement system adopts intelligent design, the overall sealing is strengthened, and it can work normally in harsh environments. An electromagnetic flowmeter with chloroprene rubber lining and molybdenum stainless steel (OCrI8Ni12Mo2Ti) electrode can be used to meet the requirements of sewage flow measurement.

When selecting, pay attention to the following points:

1) The measured liquid must be a conductive liquid or slurry;

2) Caliber and range, preferably with a normal range exceeding half of the full range (my choice is usually 4-8 times the normal flow rate), and a flow rate between 2-4 meters;

3) The pressure used must be lower than the pressure resistance of the flow meter;

4) Different lining materials and electrode materials are selected for different temperatures and corrosive media.