Reasons for unknown malfunctions in electromagnetic flowmeters during operation

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When there are problems with an electromagnetic flowmeter, the following issues need to be addressed first: 1. Check whether the operating voltage is correct, depending on the location where it is used； 2. Is the sensor grounding reliable or damaged? ； 3. Is the sensor filled with medium, and are there any bubbles in the medium? ； 4. Is the reading correct? Is the measured value within the measurement range? 5. Are the terminal connections loose? 6. Has the flow sensor been submerged in water? When there are issues with an electromagnetic flowmeter, it is necessary to pay attention to the following aspects when troubleshooting: 1. The instrument shows no display ； 2. Check whether the power is connected ； 3. Check whether the power fuse is intact ； 4. Check whether the supply voltage meets the requirements ； 5. Check whether the display’s contrast adjustment can be adjusted and whether the adjustment is appropriate. The causes of the failure include the following aspects: environmental factors ； Fluid aspects ； Installation aspect. Environmental factors: Usually, these are mainly caused by stray current interference in pipelines, strong electromagnetic wave interference in the surrounding area, and magnetic field interference from large motors. For interference caused by stray currents in pipelines, satisfactory results can usually be achieved by implementing proper separate grounding protection. However, in the presence of strong stray currents (such as those in electrolysis plants, where the peak value of the alternating voltage induced across the two electrodes can sometimes reach 1 V), additional measures are required, such as insulating the flow sensors from the pipelines. Space electromagnetic wave interference generally enters through signal cables, and is usually protected by single-layer or multi-layer shielding. Fluid-related reasons: The presence of uniformly distributed tiny bubbles in the liquid being measured generally does not affect the normal operation of an electromagnetic flowmeter. However, as the bubbles grow larger, fluctuations occur in the instrument’s output signal. When the bubbles are large enough to cover the entire electrode surface, their passage over the electrodes can cause the electrode circuit to be momentarily interrupted, resulting in even greater fluctuations in the output signal. When an electromagnetic flowmeter driven by a low-frequency square wave is used to measure slurries with too high a solid content, slurry noise is also generated, causing fluctuations in the output signal. When measuring a mixed medium, if flow sensing is performed before the mixture has been homogenized, it will also cause fluctuations in the output signal. An inappropriate selection of electrode materials and the medium to be measured can also affect accurate measurements due to chemical reactions or polarization effects. The electrode material should be selected appropriately based on the instrument or relevant manuals. Installation-related reasons: Faults are usually caused by the incorrect installation location of the electromagnetic flowmeter sensor; a common issue is installing the sensor at a high point in the pipeline where gases tend to accumulate ； Or installed on a vertical pipe from top to bottom, emptying may occur ； Or there is no back pressure behind the sensor, and the fluid flows directly into the atmosphere, resulting in a non-full condition within the measurement tube.