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Description of the reasons for the measurement error of the electromagnetic flowmeter

The electromagnetic flowmeter has high precision and good stability. However, some errors will occur when measuring! What is the cause of this? Here is the answer to the Liyuan flowmeter.

The liquid in the electromagnetic flowmeter tube is not overflowing, because the lack of back pressure or the poor orientation of the flow sensor device causes the liquid in the measuring tube to fail to overflow, and the fault phenomenon is different due to the degree of non-overflow and activity. If a small amount of gas is stratified or wavy in the water pipe, the fault phenomenon is reflected by the error addition, that is, the flow measurement value does not match the actual value; if the activity is a bubble flow or a plug flow, the fault phenomenon does not match the actual value. In addition, the output sloshing is also caused by the vapor phase instantaneously concealing the electrode appearance; if the gas phase portion of the flow cross-sectional area is increased in the stratified activity of the horizontal pipeline, that is, the liquid is not full, the output sloshing may also occur, if the liquid is not full The situation is severe, causing the liquid level to be below the electrode, which will show an output super fullness.

(2) The liquid contains a solid phase, and the liquid contains solids such as powder, granules or fibers, which may occur; 1 slurry noise; 2 electrode surface contamination; 3 conductive accumulation layer or insulating layer to cover the electrode or fabric; The fabric is worn or covered by deposits, and the flow cross-sectional area is reduced.

(3) Liquids that may crystallize, electromagnetic flowmeters should be used with caution, and some easily crystallized chemical materials can be measured normally under normal temperature conditions, because the conduits for transporting fluids have excellent heat insulation, which will not be maintained during heat preservation operations. Crystallization, but the measuring tube of the electromagnetic flow sensor is difficult to carry out heat insulation. Therefore, when the fluid flows through the measuring tube, it is easy to cause a solid layer on the inner wall due to the temperature drop. Because the flow meter measurement with other principles also has the same crystallization problem, in the absence of other better methods, an "oring" electromagnetic flow sensor with a very short measuring tube length can be selected, and the flow meter is used. The upstream pipeline is heat-insulated to be strengthened. In the pipeline connection method, it is convenient to disassemble and disassemble the flow sensor, and it can be easily removed and protected once crystallization.

(4) Problems caused by improper selection of electrodes and grounding ring materials. Electromagnetic flowmeters that are in contact with the medium due to mismatch between the raw materials and the measured medium have electrodes and grounding rings. If the matching is not correct, except for corrosion resistance, It is the appearance of the electrode. Appearance effects should be: 1 chemical reaction (formation of blunt film formation, etc.); 2 electrochemical and polarization phenomena (potential generated); 3 catalyst effect (the surface of the electrode generates aerosol, etc.). Grounding rings also have these effects, but the impact is less.

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