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How to troubleshoot problems with electromagnetic flowmeters: 1. Check whether the operating voltage is correct based 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 exposed to water? How to troubleshoot problems with electromagnetic flowmeters: 1. No display on the instrument ； 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 failures in electromagnetic flowmeters include the following aspects: environmental factors ； Fluid aspects ； Installation aspect. Environmental factors: These usually include interference from stray currents in pipelines, strong electromagnetic waves in the surrounding area, and the magnetic field generated by 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 necessary, including 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 a high 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. Reasons related to installation: Faults are usually caused by the incorrect installation location of the electromagnetic flow meter; a common issue is installing the sensor at points in the pipeline where gases tend to accumulate ； Or installed on a vertical pipe from top to bottom, evacuation 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. Methods for troubleshooting electromagnetic flowmeters: resistance method ； Current method ； Voltage method ； Substitution method ； Analog signal method ； Waveform method. Resistance method: (1) Connection and disconnection of the power fuse and excitation fuse of the flow meter; (2) Connection and disconnection of the signal cable and excitation cable of the electromagnetic flow meter; (3) Connection and disconnection of the excitation coil of the electromagnetic flow meter as well as its resistance value; (4) Insulation resistance of the excitation coil of the electromagnetic flow meter relative to ground; (5) Measurement of electrode symmetry; (6) Insulation resistance of the electrodes relative to ground ； (7) Resistance value of the flow meter power transformer. Current method: Measure the output current and excitation current of the flow meter. Voltage method: Determine the operating power supply. Substitution method: Swap the converter and amplifier board of the flow meter. Analog signal method: Use an analog signal generator to provide a flow signal in order to test the flow sensor. Waveform method: Test the waveforms at key points based on an understanding of the circuitry. The inspection items for electromagnetic flow meters include: visual inspection, testing of the converter’s characteristics, calibration of measurement values, measurement of voltages across various components, measurement of insulation resistance, and verification of the circuitry. During the inspection and adjustment of instruments, zero drift makes it very important to adjust the zero point (\"online zeroing\" requires the flow of the medium being measured to stop, which is difficult to achieve in practice). Therefore, online inspections often omit checks related to the operation of sensors, and only perform calibration of the converter in order to compare the results of the online inspection with historical data and determine whether the instrument should continue to be used, repaired, or replaced. As for the sensors, whether to replace them is decided based on the degree of degradation in the insulation resistance of the measured excitation coils. Verify whether there are any abnormalities in the electromagnetic flowmeter through online inspection. For pipelines where the medium flow cannot be stopped, the flow sensor and the converter are inspected separately; the converter is tested using analog signal generators and other standard instruments to ensure high calibration accuracy (which depends on the accuracy of the analog signal generators). As for the sensor, inspections involve testing the electrode’s resistance to liquid contact, checking the insulation resistance and copper resistance of the excitation coil including its connection cables, as well as examining the excitation current output by the converter and verifying the magnetic field strength through indirect methods. For pipelines where the medium flow can be stopped, access can be obtained through an access hole pre-installed near the sensor to inspect and clean the electrode and lining for contamination/deposition. Zero-point check of the entire electromagnetic flowmeter: The measurement tube of the flow sensor should be filled with liquid with no flow present. In many industrial settings, such conditions are not available, so the zero-point check and adjustment of the entire device are skipped; instead, a separate zero-point check and adjustment can be performed on the converter. Technically, this is only meaningful after the sensors have been inspected, and it is ensured that the insulation resistance of both the sensor excitation circuit and the signal circuit is normal (including the cables); otherwise, the entire system cannot operate properly. Typically, the individual zero point of the converter is negative, and the value is also very small ； If its absolute value is greater than 5% of the full scale, an inspection is required first; adjustments should be made after the cause has been identified. Under normal circumstances, the difference between the zero point of the entire electromagnetic flowmeter and the zero point of the converter alone is less than 1%. In many cases, zero-point differences greater than 5% are caused by the user performing incorrect zeroing operations when the pipeline valves are not properly closed. Inspection of the connection cable for electromagnetic flowmeters: This inspection involves checking the insulation resistance of each core of the signal wire and the excitation wire, as well as verifying whether the shielding layers are properly grounded. Check of the electromagnetic flowmeter converter: This check involves using general-purpose instruments and analog signal generators compatible with the flowmeter model to replace the sensor in order to provide a flow signal for zeroing and calibration. Calibration includes zero-point check and adjustment, setpoint check, excitation current measurement, current/frequency output check, etc. It should be noted that the inspection values must be compared with the previous inspection values (or factory values) to determine whether there are any changes, and whether such changes meet the original measurement requirements. Electromagnetic flowmeter sensor inspection: Check the copper resistance of the excitation coil ； Check the insulation resistance of the excitation coil ； Check the electrode contact resistance ； Check the polarization voltage between the electrode and the liquid ； Check the insulation of the signal circuit and the insulation between the excitation circuit and the signal circuit. For more information, please visit the company’s official website at http://www.yb1518.com/. Please retain this link when reproducing the content!