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What if the sewage electromagnetic flowmeter has noise on the pipeline?

There are several reasons for the occurrence of sewage fluid noise. Let us explain in detail below.

1. The fluid inside the pipe rubs the lining and the electrode, and the positive and negative ions occurring in the fluid are separated from the electrolyte fluid. The coarser the lining and electrode surfaces, the higher the free ion concentration. A part of the ions move toward the electrode due to the electric field of the electrode signal, forming a noise voltage. This noise is called flow noise. Flow noise is more prominent in low conductivity measurements. The flow noise is related to the strength of the external electric field. The larger the induced signal at high flow rate, the larger the noise amplitude and the more unstable the output.
2. The corrosion resistance of the stainless steel electrode inside the electromagnetic flowmeter has an extremely thin passivation layer on its surface, so that the electrochemical reaction reaches an equilibrium state. Solids in the fluid strike the electrode, causing the passivation layer on the electrode surface to be destroyed, losing the electrochemical balance. Contact of the metallic material with the fluid medium has the ability to restore the surface passivation layer to maintain an electrochemical balance. During the electrochemical equilibrium, free ions in the metal and fluid undergo an electrochemical reaction under the action of the signal electric field. The solid particles strike the electrode and continuously destroy the protected passivation layer; the electrochemical reaction repeatedly generates a passivation layer, so that the potential between the electrodes is continuously changed greatly, and the potential of the change causes fluid noise in the flow signal. This situation is also known as slurry noise in electromagnetic flowmeters. Theory and practice have shown that increasing the frequency of the electric field change of the electrochemical reaction signal can cause the fluid noise amplitude to decrease rapidly. This is why high frequency excitation and dual frequency excitation can solve the slurry measurement.
3. Since the thickness of the laminar boundary layer of the high-flow flowing fluid near the lining and the electrode portion becomes very thin, the roughness height of the lining and the electrode breaks through the thickness of the laminar boundary layer of the flow velocity, and the fluid hits the roughness height and the flow rate occurs. Divergence and mutation. A part of the flow rate component that is the same (or opposite) to the central axis of the measuring tube is greatly affected by the signal weight function and has a large positive error, which is the high-end flow noise.
4. The abrupt change of fluid conductivity and pH will also form flow noise, and the measurement instability of the dosing of the upstream flow meter is a typical example. The reason is that when the different media are mixed unevenly, the positive and negative ions are easily separated in the fluid. Due to the electric field of the electrode signal, a part of the ions will move toward the electrode, forming a flow noise voltage, resulting in unstable output.
It can be seen that the flow noise and the high-end flow noise in the above fluid noise are directly related to the lining of the measuring tube and the surface roughness of the electrode, and the slurry noise generated by the polarization voltage is also closely related to the surface roughness of the electrode. So it is more important to find the problem, and then you can reduce the noise generated by the flowmeter.

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