• Operation interface: mobile APP (Android, iOS)
• Smart Intelligent LCD display function
• Display Interface: English or Chinese
• Easy to Setup and install/Variety of sizes range.
• High Accuracy:±1.5% of reading(RD)
• Flow direction function: Plus or Reverse
• Alarm Function: Excitation and No fluid tubes Alarm.
• Install Way: Adjustable and Flange type.

Electromagnetic flowmeter

Flow measurement plays a very important role in fluid transport networks (e.g. gas pipelines, oil pipelines) and in all industrial equipment that needs to control the amount of fluid involved in processes such as in internal combustion engines, chemical reactors ...

Ever since the invention of the Woltman-style turbine flowmeter in the 1970s, automation experts have been eager to expect a flow meter for all other applications. But unfortunately, even though we already have 12 different flow measurement technologies, none of them can be applied to every application.
One of the most widely used methods in most applications, across most industries and with greater accuracy than the differential pressure measurement, is the electromagnetic flowmeter. According to Jesse Youder's studies, the flowmeter accounts for $ 4.7 billion in sales but the electromagnetic flowmeter accounts for only about 20% of them.
There are many electromagnetic flow meters produced every year. This device is used in all industrial processes: water, sewage, and mineral deposits, food and pharmaceuticals. This device is designed in treatment systems for almost all countries of chemical origin and coal sludge; resistant to wear, scratches and even cleaning the inside surface of pipes (designed for epidemiological hygiene applications).
Electromagnetic flowmeters are most widely used because the size of the meter can vary in size according to application requirements. Zuider Zee Company in the Netherlands was the first to use this technology for the sewer in the 1950s. Often the supplier produces products of size from
12mm to 914mm. Other brands can be supplied in sizes up to 3,048mm. Increasing or reducing such pipe size is directly related to the technology.

Principle of operation
In 1831, Michael Faraday discovered the law of electromagnetic induction, which was later named Faraday. In an electromagnetic flow meter, the coil is placed parallel to the flow and at the right angle inside the duct, there are a series of electrodes, creating a static magnetic field. The pipelines must be non-magnetic material, the inner surface of the pipe covered with insulators. As fluid flows, a small voltage appears on the electrodes. This voltage is proportional to the deviation of the magnetic field.
Modern electromagnetic flow meters operate based on a DC convertible DC field with the principle of no noise (probably from RFI, EMI and real electrical noise during fluid flow measurement). It works by turning off the magnetic field, measuring the voltage stored on the electrodes; then turn the magnetic field back on and subtract the values ​​at the on and off for each other. This mechanism is implemented several times a second to eliminate drift, zero offset.
This means that the induced voltage on the electrodes is directly proportional to the average velocity in the pipe; This method is much more accurate than other velocity measurement methods.
Electromagnetic flow meters measure the velocity with considerable accuracy, accessible with the accuracy of the position measuring device. They are often used when measuring flow applications over a relatively long period. The accuracy of the electromagnetic flowmeter is 0.5% of the measured value (within the range of 0.1 to 10m / s). Some vendors say that accuracy is still up to 0.1%.
Use electromagnetic flowmeter
Electromagnetic flowmeters have a wide range of applications that can be said to be easier to tell where the electromagnetic flow meter is not working than to list all the applications of this device.
Electromagnetic flowmeters will not work well when the pipes are not full of fluid (except for some specifically designed for this application). Failure to fill the tube will cause a significant error. One of the most common examples of improper use of the electromagnetic flowmeter is the fluid flowing along the gravity vector to the air in a water tank. Another very common phenomenon is that the flow is very slow, the pipe is not full of water and the results obtained from the electromagnetic flowmeter will be wrong. Sometimes to reduce this phenomenon, it is possible to design a U-shaped tube to ensure the water in the pipe is always full.
Electromagnetic flowmeter will not work well when the pipes are full of gas or air. The reason is to change the calculation of pipe volume and change the flow volume through the measuring device.
The electromagnetic flow meter will not work well if the flow starts and stops continuously because there is a delay between the flow starting and the indicator velocity indicated by the measuring device. This means that the electromagnetic flowmeter does not work well under conditions of continuous, repeated operation for short periods. In fact, there are exceptions for some special applications that will be designed to be able to respond very quickly.
Electromagnetic flowmeters do not provide information about the mass of flowing fluid but, when combined with a density measuring device, can provide highly accurate information. The combination will be good if the size of pipe size is 300mm. Applications of this type are quite common in the industry of mining or dredging rivers and harbors.
Most importantly, the electromagnetic flow meter will not work if the fluid is magnetic or the gas flow must be measured. The minimum conductivity of the permissible fluid is 5μS (microSiemens). In practice, it is not good to use an electromagnetic flowmeter to measure the velocity of a fluid with low average conductivity. The reason is because the internal resistance of the sensor must be much smaller than the input resistance of the measuring device.
Finally, the electromagnetic flowmeter will also work poorly if the fluid has a very high conductivity (brine or sea water). With these special applications, there is also a need for appropriate designs.

Use electromagnetic flowmeter
There are some simple rules for using an electromagnetic flow meter, which, if you follow it, will be highly effective.

Straight pipe fitting
The electromagnetic flowmeter needs to run a straight pipe less than most other electromagnetic flowmeters, usually 3.D in the opposite direction of the electrode plane and 0.D in the opposite direction. However, there are cases when pipelines with as many straight lines as possible, such as eddy phenomena, can occur in pipelines hundreds of D long in the case of a three-way turn error. These errors can cause serious errors in the measurement results, sometimes up to 40% of the measurement value.
Mount the electromagnetic flow meter vertically
One of the ways to ensure the user installs the meter correctly is to install the electromagnetic flowmeter so that the flow is vertical. This is useful for limiting whirlpools and can also help reduce airflow.
Choose the right measuring range
Although an electromagnetic flowmeter will operate over a range of 0.09 to 10m / s, it is best not to operate the device under conditions of maximum or minimum velocity measurement. In some applications there is solids in the duct that will be able to build up inside the tube, even on the electrodes. If a precipitation occurs in the duct, the calculation of the volume of the transmitted fluid will be wrong and if the aggregation on the electrode not only results will be wrong, it may damage the device. The best condition for an electromagnetic flowmeter is to operate at 60% of the maximum measured value.
Grounding the device
Note that the segments in the tube of the electromagnetic flowmeter must be non-conductive to ensure that the circuit operates correctly. Therefore, when installing the electromagnetic flowmeter, the grounding is not to be missed.
Temperature and pressure
Electromagnetic flowmeters are designed to work at moderate temperatures and pressures, and should not be emphasized in technical descriptions.
Electromagnetic flowmeters have been one of the most widely used technology lines in the 50 years since they were first introduced. They are simple and because the electromagnetic flowmeter has no moving parts, it is capable of operating for years without any maintenance or maintenance is simple.
Khanh Linh (According to globalcontrol.com)

No. 105 (June 2009) ♦ Automation today