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Electromagnetic flowmeter failure phenomenon and inspection process introduction

Common fault phenomena of electromagnetic flowmeters are: (1) no flow signal; (2) output sloshing; (3) zero point instability; (4) flow measurement value does not match actual value; (5) mountain transmission signal super fullness value 5 Classes are discussed below in sections.
Usually check the entire measurement system and the procedure for judging the fault. The inspection includes the sensor and converter of the electromagnetic flowmeter itself, the cable connecting the two, the process pipe of the electromagnetic flowmeter, and the lower (rear) position of the instrument connection cable.
The frequently used inspection methods or methods and their inspection contents are listed below:
(1) General routine instrument inspection
1 resistance method ● fuse on and off
●Switching of signal cable and excitation cable
●On and off of the excitation coil
●Electrode symmetry measurement
●Insulation resistance of the electrode to the ground
●Insulation resistance of the excitation coil to the ground
2 current method ● measure the excitation current
●Measure the output current
3 voltage method ● Discrimination: Is the working power supply (including the power supply and the converter's own power supply) correct?
4 Waveform method ● Measure key point waveforms on the basis of familiar lines, and identify the fault location

(2) Alternative method The interchangeability between the converter and the sensor and the components of the converter's internal circuit board is used to determine the location of the fault by an alternative method.
(3) Signal trace method Replace the sensor with an analog annunciator to provide a flow signal under the condition that the liquid is not flowing to test the electromagnetic flow converter.
● Checking starts from the direction in which the display meter works normally, and the direction of reverse flow signal transmission. The converter is tested with an analog annunciator to determine that a fault has occurred in the converter and its post-position instrument is still in the upper sensor of the converter. If the converter is faulty, if it is conditional, it can be conveniently borrowed from the converter or the circuit board inside the converter for debugging. If the sensor needs to be replaced, it must be stopped and the pipeline system is closed. Do it. Especially for large-caliber flow sensors, the amount of trial and change engineering is large. Usually, after completing other inspections, the final determination is made to remove the pipeline to check the internal condition of the measuring tube or exchange.

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