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Since electromagnetic flowmeters were put into industrial use in the 1950s, they have been applied in industrial production. China began developing them in 1957, and today it is capable of producing electromagnetic flowmeters of various diameters, ranging from 25 to 1200 millimeters. With the development of industrial production and the improvement of energy management, electromagnetic flowmeters have gradually attracted people’s attention. Industrial and mining enterprises consume large amounts of water and energy, and in the past, such usage was often not measured. Currently, in the efforts to strengthen energy management, clear requirements have been set for water metering. Our factory uses water from Dianchi Lake as production water, with a monthly consumption of around 400,000 cubic meters. Due to the poor water quality, sediment, shells, weeds, as well as dead fish and shrimp often come to the surface as well. In the past, rotary water meters were installed for measurement purposes, but they became clogged shortly after installation and could no longer be used, turning water measurement into a persistent problem. In 1981, experiments were conducted using electromagnetic flowmeters for measuring production water, and certain results were achieved. An electromagnetic flowmeter operates on the principle of Faraday’s electromagnetic induction. The instrument utilizes a conductive liquid that moves perpendicular to the magnetic field lines in an alternating magnetic field; as the conductive liquid cuts through these magnetic field lines, an induced electromotive force E is generated. This force is related to the flow velocity V of the liquid in the magnetic field (in centimeters per second), the magnetic flux density B (in gauss), and the inner diameter D of the measuring conduit. The instantaneous flow rate Q (in cubic centimeters per second) is equal to the product of the flow velocity V and the cross-sectional area A of the conduit (in square centimeters). Here, K is a constant specific to the instrument. By feeding E into the converter and undergoing appropriate amplification and transformation, a signal proportional to the flow rate can be output. From March to August 1981, our factory installed five instruments at the water usage points in four workshops; each instrument was equipped with a DX S-102 integrator. These instruments were used to measure the water used in production, under normal temperature conditions, with a conductivity of 1.2x10-3 mho. The proper functioning of electromagnetic flowmeters depends not only on quality issues but also greatly on their selection and installation. Electromagnetic flowmeters can measure liquids with a conductivity greater than 10-5 to 10^-6 (mho-centimeters)^-1. The conductivity of ordinary well water and river water is around 10-4 (ohm-cm). The production water used in our factory has a resistance of about 1.2, 10_1 (ohm-cm), while the domestic water has a resistance of around 4.16x 1j)-4. Electromagnetic flowmeters cannot be used to measure liquids containing ferromagnetic substances, as this may cause measurement errors. Because the maximum operating pressure of the gauge is 16 kgf/cm²; if the pressure of the medium being measured is too high, the transmitter may leak. The typical operating flow rate is chosen to be around 50% of the instrument’s measurement range. The flow rate is generally set between 2 and 4 meters per second. During installation, it should be noted that since the transmitter’s output signal is only a few millivolts, it should be placed away from electrical equipment such as transformers, motors, and cables, in order to avoid interference from strong electric fields. It should be installed in a location that is easy to maintain and where there is minimal vibration, and contact with corrosive gases and liquids should be avoided as much as possible. The transmitter can be installed either horizontally or vertically; the conduit must be filled with liquid, otherwise significant errors will occur. There should be a straight section of pipe 5 times the diameter of the tube in front of the transmitter, so that maintenance work does not affect water supply, and a bypass valve should be installed. It should be used in accordance with the manufacturer’s specifications – random connections will result in errors. This is different from other instruments: the distance between the transmitter and the converter should be within 15 meters. The connection cables should be shielded by conduits, and the power, excitation, and signal cables should each be run in separate conduits. The transmitter must have a proper independent grounding system. The instrument should have rain protection, good drainage, and must not be exposed to water. When the instrument is installed or after it has been in use for some time, the grounding resistance should be measured, which can be done using a grounding resistance tester. The resistance values of each pole of the transmitter to ground (the earth’s surface) are measured using a 500-volt megohmmeter. The signal pole resistance to ground (when the inner wall of the transmitter is dry) should be greater than 100 megohms, and the excitation pole resistance to ground should be greater than 10. Megohm. Our factory currently uses electromagnetic current analog signal generators to check the performance of the converters, but they cannot be used to determine whether the flow rate is accurate. The signal from electromagnetic flowmeters is very weak, and excessive interference voltages can prevent the instrument from functioning. Therefore, a interference voltage tester is used for measurement, and the instrument is adjusted based on the measured values to minimize the interference voltage. The advantages of electromagnetic flowmeters include a simple structure for the transmitter, strong adaptability to various liquids – any liquid with a certain degree of electrical conductivity can be measured – and a wide range of models available; sizes ranging from 25 to 1200 millimeters are currently offered. The flow range ratio (maximum flow/minimum flow) is high, often reaching several dozen; in our factory, this ratio is 5 to 25. These flowmeters have low pressure loss, respond quickly, and allow the flow signal to be transmitted over long distances. The instrument outputs a signal of 0 to 10 milliamps, which can be used in combination with electric display units. }The measurement is accurate, and no blockage will occur. The disadvantages include poor interference resistance, high installation requirements, limited overvoltage tolerance of the converter, and components that are prone to damage. Due to limitations in the insulation material of the transmitter, it is not possible to measure media with temperatures above 600°C. The transmitter and converter must be used together; interchangeability is low, and once either one is damaged, the entire unit has to be replaced. Additionally, the cost of these instruments is high. After several months of trial operation, the electromagnetic flowmeter has performed fairly well. Having a clear understanding of energy management facilitates corporate management and promotes water conservation in workshops; after the installation of meters, water usage in these workshops decreased by one-third to two-thirds. The electromagnetic flowmeter transmitter is a straight tube without any protruding measuring elements, and no blockages have occurred to date, which reduces the amount of maintenance required. Due to the large fluctuations in the demand for water for production, it is necessary to achieve accurate measurement both at high flow rates and low flow rates. Sometimes the range ratio can reach 25, and the meter still gives accurate readings; whereas the range ratio of throttle devices is generally only around 3. The entire set of instruments is carefully calibrated and verified for actual flow rates before leaving the factory; as long as they are installed properly and connected correctly, they can generally be put into operation without any further adjustments. Generally, the maintenance workload for transmitters is low, and converters usually do not require constant attention. However, converters are assembled using transistor components, and the selection of certain components may not be appropriate, which often leads to breakdowns and renders the instrument inoperable. For more information, please visit the company’s official website at http://www.yb1518.com/. Please retain this link when reproducing the content! http://www.yb1518.com/UploadFiles/2012717174126829.jpg