Electromagnetic flowmeters study fluid noise, explore the causes of the noise, find ways to reduce fluid noise, and improve sensor signal-to-noise ratios, especially for weak excitation currents (electromagnetic water meters, two-wire electromagnetic flowmeters) and low flow rates ( The expansion of the flow measurement range at high flow rates (above 0.1 m/s) and high flow rates (above 15 m/s) is of great significance.
The causes of fluid noise are as follows:
1. Fluid friction lining and electrodes, the positive and negative ions occurring in the fluid are separated from the electrolyte fluid. The rougher the lining and electrode surface, the higher the free ion concentration. Due to the electric field of the electrode signal, a part of the ions will move toward the electrode to form a noise voltage. Such noise is called flow noise. Flow noise is more prominent at low conductivity measurements. The flow noise is related to the strength of the external electric field. When the flow rate is high, the larger the inductive signal, the greater the noise amplitude and the unstable output.
2. The rapid changes in fluid conductivity and pH will also create flow noise. The measurement of instability in the upstream of the meter is a typical example. The reason is that when different media are mixed unevenly, the positive and negative ions can be easily separated in the fluid. Due to the electric field of the signal from the electrode, part of the ions will move to the electrode, forming a flow noise voltage and causing instability of the output.
3. The thickness of the laminar boundary layer near the lining and the electrode becomes very thin due to the high flow velocity of the flowing fluid. The roughness of the lining and the electrode highly breaks through the thickness of the laminar boundary layer of the velocity flow. The fluid hits this part of the roughness height and the flow velocity occurs. Divergence and mutation. Some of the velocity components that are the same (or opposite) to the central axis of the measuring tube are affected by the signal weight function, which has a great influence on the electrode signal and forms a large positive error. This is the high-end flow noise.
The flow noise and the high-end flow noise in the above fluid noise are directly related to the roughness of the lining and the electrode surface of the measuring tube, and the slurry noise generated by the polarization voltage is also greatly related to the surface roughness of the electrode. Changzhou Chengfeng electromagnetic flowmeter , the domestic high-end flow meter brand, to meet customer needs first, quality first, allowing customers to use the rest assured.
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