Electromagnetic flowmeter (EMF for short) is a new type of flow measuring instrument developed rapidly with the development of electronic technology in the 1950s and 1960s. Electromagnetic flowmeters are inductive instruments that are manufactured according to Faraday's law of electromagnetic induction to measure the volumetric flow of conductive media in tubes.

First of all, we need to understand the structure of the electromagnetic flowmeter. It is mainly composed of the magnetic circuit system, measuring catheter, electrode, housing, lining and converter. Now we will analyze the various parts of it gradually, as follows:

Magnetic circuit system: Its role is to produce a uniform DC or AC magnetic field. The DC magnetic circuit is realized by a permanent magnet. The advantage is that the structure is relatively simple and less disturbed by the AC magnetic field, but it is easy to polarize the electrolyte liquid in the measurement conduit so that the positive electrode is surrounded by negative ions and the negative electrode is positive ions. Enclosing, that is, the polarization phenomenon of the electrode, and resulting in an increase in the internal resistance between the two electrodes, thus seriously affecting the normal operation of the instrument. When the pipe diameter is larger, the permanent magnet is also relatively large, heavy and uneconomical, so the electromagnetic flowmeter generally uses an alternating magnetic field, and is generated by 50HZ power frequency power supply excitation.

Measuring catheter: Its role is to allow the measured conductive liquid through. In order to make the magnetic flux to be diverted or short-circuited when passing through the measuring tube, the measuring tube must be made of non-magnetic material, low conductivity, low thermal conductivity, and a certain mechanical strength. Stainless steel, glass fiber reinforced plastic, high strength without magnetic permeability Plastic, aluminum and so on.

Electrode: Its role is to derive and be measured in proportion to the induced potential signal. The electrodes are generally made of non-magnetic stainless steel and are required to be flush with the lining so that the fluid passes unimpeded. Its installation position should be in the vertical direction of the pipeline to prevent deposits from accumulating on it and affect the measurement accuracy.

Enclosure: Made of ferromagnetic material, it is a housing that distributes the excitation coil and isolates the interference from external magnetic fields.

Lining: There is a complete, electrically insulating liner on the inside of the measuring tube and on the flange sealing surface. It is in direct contact with the liquid to be measured. Its role is to increase the corrosion resistance of the measuring tube and prevent the induced potential from being short-circuited by the metal measuring tube wall. Lining materials are mostly corrosion-resistant, high-temperature resistant, wear-resistant polytetrafluoroethylene plastics, ceramics and so on.

Converter: The induced potential signal generated by the liquid flow is very weak, and is greatly affected by various interference factors. The role of the converter is to amplify and convert the induced potential signal into a unified standard signal and suppress the main interference signal. Its task is to amplify the induced potential signal Ex detected by the electrode into a uniform standard DC signal.

Second, its characteristics include the following aspects:

1. There are no obstructed flow components in the measuring tube, no pressure loss, and the straight tube section requires less. Unique adaptability to slurry measurements

2. The measurement is not affected by changes in fluid density, viscosity, temperature, pressure, and conductivity;

3 converter uses a novel excitation method, low power consumption, zero stability, high accuracy. Flow range up to 150:1;

4. A reasonable choice of sensor lining and electrode materials, that is, a good corrosion resistance and wear resistance;

5. The converter adopts 16-bit high-performance microprocessor, 2x16 LCD display, convenient parameter setting and reliable programming;

6 Converter can be integrated with the sensor or separate type;

7. The measurement accuracy is not affected by changes in fluid density, viscosity, temperature, pressure, and conductivity. The sensor-induced voltage signal is linearly related to the average flow velocity, so the measurement accuracy is high.

8. The flow meter is a two-way measurement system with three totalizers: forward total, reverse total, and total differential; positive and negative flow can be displayed, and multiple outputs: current, pulse, and digital communication , HART;

9. There is no flow blockage in the measurement pipe, so there is no additional pressure loss; there are no moving parts in the measurement pipe, so the sensor life is extremely long.

10. The converter uses surface mount technology (SMT), with self-test and self-diagnosis functions;

11. Since the induced voltage signal is formed in the entire space filled with magnetic field and is the average value on the surface of the pipe, the straight pipe section required by the sensor is shorter and the pipe diameter is 5 times longer.

12. Two-way measurement system can measure positive flow and reverse flow. Special production techniques and high quality materials are used to ensure that the product's performance is stable over a long period of time.

13. The converter adopts internationally very good single-chip microcomputer (MCU) and surface mount technology (SMT), with reliable performance, high precision, low power consumption, stable zero point and convenient parameter setting. Click Chinese to display the LCD and display the cumulative flow, instantaneous flow rate, flow rate, and flow rate percentage.

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