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Among them, large-diameter electromagnetic flowmeters are widely used in water supply and drainage projects. The application areas of electromagnetic flowmeters include large-diameter, medium and small-diameter, small-diameter, and micro-diameter types. Medium and small diameter pipes are commonly used in situations involving difficult-to-measure fluids with both solid and liquid phases, or in applications that require high standards of cleanliness; examples include measuring pulp and black liquor in the papermaking industry, slurry in the non-ferrous metal industry, coal slurry in coal processing plants, highly corrosive liquids in the chemical industry, controlling the cooling water flow at furnace tuyeres in the steel industry, and measuring and controlling the flow rate of coal transported over long distances through pipelines. Small and ultra-small diameter pipes, on the other hand, are typically used in industries such as pharmaceuticals, food processing, and bioengineering, where hygiene standards are crucial. 1.2 Accuracy and other features of electromagnetic flowmeters: Some models offer high accuracy and numerous functions, while the performance of general-purpose EMF devices on the market varies significantly. Some have low precision and simple functions. The basic error of instruments with high precision is (±0.5%±1%R), while that of instruments with lower precision is (±1.5%±2.5%FS); the price difference between them is 12 times. Therefore, in applications where high measurement accuracy is not required (for example, in non-commercial accounting situations where reliability and good repeatability are sufficient for control purposes), it is not economical to use instruments with high precision. The basic error is only (±0.2% ± 0.3%R), but strict installation requirements and reference conditions apply; some models of electromagnetic flowmeters claim to have even lower errors. For example, at an ambient temperature of around 2022°C, the required lengths of the straight sections before and after the sensor are typically greater than 10D and 3D respectively; often they are 5D and 2D. It is also recommended that the flow sensor be calibrated with actual flow using the straight sections before and after it on a flow calibration device, in order to reduce errors caused by interference. Therefore, when comparing different models, one should not rely solely on specifications; instead, it is necessary to read the manufacturer’s catalogs or manuals in detail for a comprehensive analysis. Simply put, it involves measuring one-way flow, and there are significant differences in the EMF functions available on the market. Only analog signals are used to drive the instruments in the rear section ； The multi-functional meter features the ability to measure two-way flow, range switching, upper and lower flow limit alarms, empty pipe and power outage alarms, small signal rejection, flow display and total volume calculation, automatic verification and self-diagnosis of faults, communication with a host computer, and motion configuration. Some models of instruments offer a serial digital communication function with various communication interfaces and dedicated chips (such as ASICs for connecting to HART protocol systems, PROFINET, Modbus, CONFIGFF fieldbuses, etc.). 1.3 The flow rate, full-scale flow rate, range, and diameter of the electromagnetic flowmeter shall be determined based on the flow volume. In the process industry, liquids with different viscosities such as water are transported, and the diameter of the instruments selected can vary but remains the same as that of the pipes. The flow velocity in pipes is generally the economic velocity of 1.53 m/s; when an EMF is used in such pipes, the sensor diameter can be the same as that of the pipe. For fluids containing substances prone to adhesion, accumulation, and scaling, a flow rate of not less than 2 m/s and up to 34 m/s or higher is recommended, which helps with self-cleaning and prevents adhesion and deposition. Used for highly abrasive fluids such as slurry; the recommended flow rate should be below 23 m/s to reduce wear on the lining and electrical components. 1.4 Liquid conductivity of electromagnetic flowmeters: A prerequisite for using an EMF is that the liquid being measured must be conductive, and its conductivity must not be below a certain threshold (i.e., the minimum value). A conductivity below the threshold results in measurement errors that make it unusable; whereas when above the threshold, measurements can still be taken with little variation in the indicated error. The threshold for general-purpose EMFs ranges from 10-4 to (5×10-6) S/cm, depending on the model. In use, it also depends on the length of the signal line connecting the sensor and the converter as well as its distributed capacitance; the manufacturer’s instructions typically specify the length of the signal line corresponding to a certain conductivity. Instruments that use non-contact capacitive coupling for large-area electricity measurement can detect liquids with a conductivity as low as 5×10-8 S/cm. The conductivity of industrial water and its aqueous solutions is greater than 10-4 S/cm, while that of acids, bases, and salts ranges from 10-4 to 10-1 S/cm; in these cases, there are no issues with their use. Low-purity distilled water has a conductivity of 10-5 S/cm, and again, there are no problems with it. Petroleum products and organic solvents cannot be used if their conductivity is too low. Table 1 lists the conductivity of several liquids. According to available information, some pure liquids or aqueous solutions have low conductivity and are considered unsuitable for use. However, in practical applications, it is possible to use them despite the presence of impurities that increase their conductivity. For aqueous solutions, the conductivity values listed in the data were measured in the laboratory using pure water as a base; however, the actual solutions used in practice may be prepared with industrial water, in which case the conductivity will be higher than the values given, which is also advantageous for flow measurement. 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