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Classification based on whether the sensor electrodes of electromagnetic flowmeters are in contact with the liquid being measured: 1. Contact-type electrodes – The electrodes that are in contact with the liquid represent the traditional design for EMF flowmeters; usually, there is a pair of such electrodes, while larger-diameter instruments use two pairs. The non-full-pipe EMF also uses 3 pairs of motors or strip electrodes. 2. Non-contact electrodes – Large-area electrodes are attached closely to the outer surface of the lining (or insulated measurement tube), and flow signals are detected through capacitive coupling; this type of electromagnetic flowmeter, which uses capacitive detection, is also known as a capacitive electromagnetic flowmeter. The preamplifier is located inside the sensor and relies solely on the electrodes; the excitation frequency is higher than that of ordinary EMFs, at 50/2 Hz, with some cases reaching over 100 Hz. Instruments of this type do not generate noise resulting from electrode surface effects such as electrode passivation, oxidation, and catalytic action; there is also no chance of flow noise or slurry noise. Covering the inner surface of the lining with a non-conductive layer such as grease or a thin insulating layer also does not affect the measurement ； However, if the covering layer is a conductive film, the instrument will give no indication. Some instrument manufacturers abroad refer to this type of instrument as electrodeless electromagnetic flowmeters. The advantages of electromagnetic flowmeters are as follows: 1. Electromagnetic flowmeters use a smooth straight pipe without any flow-obstructing components as the measurement channel. This type of pipe is chosen because it is not prone to blockage and is suitable for measuring liquid-solid two-phase fluids containing solid particles or fibers, such as pulp, coal water slurry, mineral slurry, mud, and sewage. 2. Electromagnetic flowmeters do not cause pressure losses due to flow measurement; the resistance of such instruments is merely that of a pipe of the same length, resulting in significant energy savings. They are thus most suitable for large-diameter water supply pipes where low resistance losses are required. 3. The volumetric flow rate measured by electromagnetic flowmeters in practice is actually not significantly affected by changes in fluid density, temperature, pressure, viscosity, and conductivity (as long as they remain above a certain threshold). 4. Compared with most other flow meters, electromagnetic flowmeters require a shorter straight pipe section in front of them. 5. Electromagnetic flowmeters have a large measurement range, typically 20:1 to 50:1, offering a wide selectable flow range. The full-scale liquid flow rate can be selected within the range of 0.5 to 10 m/s. Some models of meters allow the flow rate to be increased or decreased on-site as needed (for example, they are equipped with 4-digit potentiometers for setting the meter constants), eliminating the need for offline calibration using a real flow meter. 6. The diameter range of electromagnetic flowmeters is wider than that of other types of flow meters, ranging from a few millimeters to 3 meters. It can measure flow in both forward and reverse directions, as well as pulsating flow, provided that the pulsation frequency is much lower than the excitation frequency. The instrument output is essentially linear. It is easy to select the material types for fluid-contact parts, and it can be used with corrosive fluids. For more information, please visit the company’s official website at http://www.yb1518.com/. Please keep this link when reproducing the content!