Electromagnetic flowmeter design and solutions

Which industrial fields use flow meters

"If you can't measure, you can't manage." This is a mantra in the industrial field, especially suitable for flow measurement. Simply put, there is an increasing demand for flow monitoring, often requiring higher speed and precision monitoring. There are several areas where industrial flow measurement is important, such as domestic waste. As people pay more and more attention to environmental protection, in order to make our world cleaner and less polluted, waste disposal and monitoring have become very important. Humans consume a lot of water, and as the population grows, the water consumption will increase. The flow meter is very important. It can not only monitor domestic wastewater, but also is an integral part of the process control system of the sewage treatment plant.

Figure 1. Sewage treatment plant sketch

flow meters are also used in many industrial control processes, including chemical/pharmaceutical, food and beverage, pulp and paper making, etc. Such applications often require flow measurement in the presence of a large amount of solids—most flow technologies cannot easily meet this requirement.

The transportation and metering field deals with product transfer and payment between two parties, requiring high-end flow meters. One example is the transportation of oil through a large pipeline system. In this kind of application, even small changes in flow measurement accuracy over time may result in a loss or significant benefit to one party.

Electromagnetic induction technology is very suitable for liquid flow measurement

For liquid flow measurement, technology has many advantages. Its sensor is generally connected to the pipe, and its diameter is the same as that of the pipe, so it will not interfere with or restrict the flow of the medium during measurement. Since the sensor is not directly immersed in liquid, there are no moving parts, so there is no wear problem.

The electromagnetic method measures volumetric flow, which means that the measurement is not sensitive to changes in fluid density, temperature, pressure, and viscosity. Once the electromagnetic flowmeter is calibrated with water, it can be used to measure other types of conductive fluids without further calibration. This is an important advantage that other types of flow meters do not have.

Electromagnetic flowmeter is particularly suitable for measuring solid-liquid two-phase media, such as mud and other high-conductivity media with suspended soil, solid particles, fibers or viscous materials. It can be used to measure sewage, mud, mineral pulp, paper pulp, chemical fiber pulp and other media. This makes it particularly suitable for food, pharmaceutical and other industries, and can be used to measure corn syrup, fruit juice, alcohol, drugs, plasma and many other special media.

The working principle of electromagnetic flowmeter

The working principle of electromagnetic flowmeter is based on Faraday's law of electromagnetic induction. According to Faraday's law, when a conductive fluid flows through the magnetic field of the sensor, an electromotive force proportional to the volume flow is generated between a pair of electrodes, and its direction is perpendicular to the flow direction and the magnetic field. The magnitude of the electromotive force can be expressed as:

Among them, E is the induced potential, k is the constant, B is the magnetic flux density, D is the inner diameter of the measuring tube, and v is the average velocity of the fluid in the measuring tube along the axial direction of the electrode section.

Figure 2. Working principle of magnetic flowmeter