Electromagnetic Flow Meter After-Sales Case 4

Field problem

The signal of electromagnetic flowmeter is abnormal, and the instantaneous flow shows negative value.

Troubleshooting and analysis 

After receiving customer feedback, the technical team of ARTang immediately communicated with customers through video and WeChat, and checked and analyzed the faults:

1. There are nine electromagnetic flowmeters on site, and the flow values of three flowmeters are negative.

2. Detect the flow direction of the measured medium, and find that the flow direction of the medium is opposite to the direction of the flowmeter arrow, resulting in negative instantaneous flow value.

Solution

When the on-site debugging is completed, the electromagnetic flowmeter shows positive and works well.

Customer feedback

After modifying the small signal cut-off point, when there is no flow in the pipeline, the number of converters is usually 0 m/s.

Why should electromagnetic flowmeter be installed vertically when measuring solid-liquid medium?

Avoid the deposition of solid particles on the sensor wall to form scale. If there is precipitation on the surface of the electrode, the electromagnetic flowmeter will affect the performance of the measuring electrode, and the different conductivity of the precipitate will cause different problems, such as:

A. If the dielectric precipitated on the surface of the electrode is not conductive, it will lead to open circuit of the electrode, and the flowmeter will not work normally.

B. If the precipitated material in the lining is conductive, such as air oxidized rust layer or metal material, and the conductivity of the precipitated material is greater than that of the measured medium, the output of the converter will be greater than the actual measured value.

C. If the deposited material in the lining is conductive, but the conductivity of the deposited material is lower than that of the medium, the indicator number of the converter will be less than the actual measured value.