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There are two types of failures that can occur in electromagnetic flowmeters during operation: one is a failure of the instrument itself, that is, failures caused by damage to the instrument’s structural components or parts； Second are failures caused by external factors, such as improper installation leading to flow distortion, deposition, and scaling. This article discusses these two types of faults. I. The instrument does not output a flow signal. 1. Cause analysis This type of fault is relatively common in electromagnetic flowmeters; the common causes include: (1) Abnormal power supply to the instrument ； (2) Abnormal cable connection ； (3) The liquid flow conditions do not meet the installation requirements ； (4) Damage to sensor components or an adhesive layer on the inner wall being measured ； (5) Damage to the converter components. 2. Solution: (1) Confirm that power is supplied, check whether the voltages output by the power circuit board are normal, or try replacing the entire power circuit board to determine its condition. (2) Check whether the cable is in good condition and the connection is correct. (3) Check the liquid flow direction and whether the tube is filled with liquid. For electromagnetic flowmeters that can measure in both forward and reverse directions, although measurement is possible when the directions are different, the displayed flow rate will indicate the wrong direction; this must be corrected. If removing the sensor is a time-consuming task, it is also possible to change the direction of the arrow on the sensor and reset the symbols displayed on the gauge. The pipes not being filled with liquid is mainly caused by an improper installation location of the sensors; measures should be taken during installation to prevent the pipes from not having enough liquid in them. (4) Check whether the electrodes on the inner wall of the transmitter are covered with a layer of liquid scum; for measurement liquids prone to scum formation, cleaning should be carried out regularly. (5) If it is determined that the fault is caused by a damaged component of the converter, simply replace the damaged component. II. Fluctuations in output values 1. Cause analysis Most failures of electromagnetic flowmeters are caused by the influence of the measured medium or the external environment; once such external interferences are removed, the fault disappears on its own. To ensure the accuracy of measurements, such faults cannot be ignored either. In some production environments, severe vibrations in the pipes or liquid can cause the circuit board of the flow meter to become loose, which in turn can lead to fluctuations in the output values. 2. Solution: (1) Determine whether it is due to process operations, resulting in actual pulsations in the flow; in this case, the electromagnetic flowmeter simply reflects the actual flow conditions, and the fault will resolve on its own once the pulsations cease. (2) Electromagnetic interference caused by external stray currents, etc. Check whether there are any large electrical appliances or welding machines in operation in the environment where the instrument is located; ensure that the instrument is properly grounded and that its operating environment is suitable. (3) When the pipeline is not filled with liquid or when there are bubbles in the liquid, both situations are caused by process-related reasons. At this point, it is possible to ask the process technician to confirm that once the tube is filled with liquid or the bubbles subside, the output value will return to normal. (4) The transmitter circuit board has a plug-in design; due to the significant vibrations in the pipelines or liquids at the measurement site, this often causes the power supply board of the flow meter to become loose. If it becomes loose, the flow meter can be disassembled and the circuit board reattached. III. The flow measurement value does not match the actual value. 1. Cause analysis: (1) Is the transmitter circuit board intact? ； (2) When the liquid flow rate is too low, the liquid under measurement contains tiny bubbles; these bubbles rise and accumulate above the pipeline, thereby changing the flow area of the liquid. In cases where there is a large amount of gas, interference signals are generated, affecting the accuracy of the measurements ； (3) Inaccurate measurements can occur due to poor connections in the signal cable, or as a result of a decrease in the cable’s insulation properties over time ； (4) The parameter settings of the converter are inaccurate. 2. Solution: (1) Check whether the circuit board of the electromagnetic flowmeter is intact. If the junction box gets wet or is corroded by corrosive liquids being measured, it can lead to a decline in the electrical equipment’s performance or even damage to it. The circuit board should be replaced at this time. (2) Ensure that the flow rate of the liquid being measured in the pipeline is above the minimum flow limit, so that the transmitter can function properly. (3) Check whether the connections of the signal cables and their insulation properties are in good condition; if the signal cables are loose, reconnect them ； If it is detected that the insulation of the cable does not meet the insulation requirements, a new cable must be replaced. (4) Reset the converter settings, and verify the converter’s zero and full-scale values. IV. Output signal exceeds the full-scale range 1. Cause analysis The reasons for such faults are roughly as follows: (1) Errors in the wiring of the signal cable or a disconnection in the cable connection ； (2) The parameter settings of the converter are incorrect ； (3) The converter and sensor models are not compatible. 2. Solution: (1) Check whether the connection of the signal circuit of the electromagnetic flowmeter is proper; if the signal circuit is disconnected, the output signal will exceed the full-scale value. In this case, the signal cable needs to be reconnected correctly. At the same time, it is necessary to check whether the insulation performance of the cable is intact; if it no longer meets the requirements, a new cable must be replaced. (2) Thoroughly check whether the various parameter settings of the converter, as well as its zero and full-scale values, meet the requirements. (3) If it is detected that the model of the converter does not match that of the sensor, it is necessary to contact the manufacturer for replacement. V. Unstable zero point 1. Cause analysis (1) The pipeline is not filled with liquid or the liquid contains bubbles. (2) Subjectively, it is believed that there is no flow of the liquid in the pump, when in fact there is slight flow. (3) Reasons related to the liquid (such as poor uniformity of liquid conductivity, electrode contamination, etc.). (4) Decrease in insulation of the signal circuit. 2. Solutions: (1) If the pipeline of the electromagnetic flowmeter is not filled with liquid or contains bubbles, this is due to process-related issues; in such cases, it is necessary to ask the process engineers to verify the situation. Once the process is operating normally, the output values will return to normal. (2) There is slight flow inside the pipe; this is not a fault of the electromagnetic flowmeter. (3) Zero drift may occur if impurities deposit on the inner wall of the measurement tube or cause scaling there, or if the electrodes become contaminated; in such cases, cleaning is necessary ； If the zero point does not change much, you can also try to zero it again. (4) Due to environmental conditions, dust, oil, and other contaminants may enter the casing; therefore, it is necessary to check whether the insulation at the electrode area has decreased or been damaged. If the insulation requirements are not met, cleaning must be carried out. For more information, please visit the company’s official website at http://www.yb1518.com/. Please retain this link when reproducing the content!