Common faults in the use of electromagnetic flowmeters, some are faults caused by damage to the components of the instrument itself, and some are faults caused by improper selection, improper installation, environmental conditions, fluid characteristics, etc., such as display fluctuations, reduced accuracy, and even instrument damage. . It can generally be divided into two types: failures during installation and commissioning (debug during commissioning) and failures during normal operation (running faults).
　　
2. Commissioning period failure
　　
Debugging expectation failures generally appear in the instrument installation and debugging phase. Once excluded, they will not appear again under the same conditions in the future. Common commissioning failures are often caused by improper installation, environmental disturbances, and fluid characteristics.
　　
1 ) Installation aspects
　　
Usually the fault is caused by incorrect installation position of the electromagnetic flow sensor. For example, the sensor is installed at the high point of the duct that is easy to accumulate gas; or it is installed on the vertical tube from top to bottom, and may be drained; or after the sensor Without back pressure, the fluid is discharged directly into the atmosphere to form a non-full tube in the measuring tube.
　　
2 ) Environmental aspects
　　
Usually mainly due to pipeline stray current interference, space strong electromagnetic wave interference, large motor magnetic field interference. Pipe stray current interference usually takes good single grounding protection to get satisfactory results, but if you encounter strong stray current (such as electrolysis shop piping, sometimes the peak potential Vpp induced on the two electrodes can be as high as 1V ), still Additional measures and insulation of the flow sensor and piping are required. Space electromagnetic interference is typically introduced via a signal cable and is typically protected by a single or multiple layers of shielding.
　　
3 ) Fluid aspects
　　
The evenly distributed microbubbles in the liquid to be tested usually do not affect the normal operation of the electromagnetic flowmeter, but as the bubbles increase, the instrument
The output signal of the meter will fluctuate. If the bubble is large enough to cover the entire surface of the electrode, the output signal will be more fluctuated as the bubble flows through the electrode and the electrode circuit will be momentarily broken.
　　
When the low-frequency square-wave excited electromagnetic flowmeter measures the solid content of too much slurry, it will also generate slurry noise, which will cause the output signal to fluctuate.
　　
When measuring mixed media, if the flow sensor is measured before the mixing is not uniform, the output signal will also fluctuate.
　　
Improper matching of the electrode material and the measured medium will also affect normal measurement due to chemical action or polarization. The electrode material should be properly selected according to the instrument selection or related manual.
　　
3. Runtime failure
　　
The fault in the running period is the fault that occurs after the electromagnetic flowmeter has been debugged and operated normally for a period of time. The common faults during the running period are generally caused by factors such as the adhesion layer on the inner wall of the flow sensor, lightning strikes and environmental conditions.
　　
1 ) Sensor inner wall adhesion layer
　　
Since electromagnetic flowmeters are commonly used to measure dirty fluids, after a period of operation, the adhesion layer is often accumulated on the inner wall of the sensor to cause a malfunction. These failures are often caused by the electrical conductivity of the adhesion layer being too large or too small. If the attachment is an insulating layer, the electrode circuit will be broken and the meter will not work normally; if the conductivity of the adhesion layer is significantly higher than the fluid conductivity, the electrode circuit will be short-circuited.
　　
The meter also does not work properly. Therefore, the fouling layer in the measuring tube of the electromagnetic flowmeter should be removed in time.
　　
2 ) Lightning strike
　　
Lightning strikes easily induce high voltages and surge currents in the meter circuit, causing damage to the meter. It is mainly introduced through the power line or the excitation coil or the flow signal line between the sensor and the converter, especially from the control room power line.
　　
3 ) Changes in environmental conditions
　　
During commissioning, because the environmental conditions are still good (for example, there is no source of interference), the flowmeter works normally, and it is often easy to neglect the installation conditions (for example, the grounding is not very good). In this case, once the environmental conditions change, a new source of interference occurs during operation (such as welding on the pipeline near the flowmeter, installing a large transformer nearby, etc.), which will interfere with the normal operation of the meter, and the output of the flowmeter. The signal will fluctuate.
　　
4. Summary
　　
In the process of using the electromagnetic flowmeter, various faults may occur, but in general, all the faults can be classified into two types, that is, the commissioning period fault and the running period fault, as long as we pay attention to this in daily work. Two kinds of faults are well solved and solved. I believe that the electromagnetic flowmeter must be able to play its due role.

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