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How to Eliminate the Noise of Electromagnetic Flow Meter?

2020-10-14
How to Eliminate the Noise of Electromagnetic Flow Meter?

 In the previous article, we mentioned the method to eliminate the noise of electromagnetic flowmeter. But today, the flowmeter manufacturer Qingtian Instrument wants to tell you that everything has a cause. We first find out the reasons for the noise, and believe that this problem can be effectively avoided later.
 
1. The fluid rubs the lining and the electrode, and the positive and negative ions generated in the fluid are separated from the electrolyte fluid. The rougher the surface of the lining and electrode, the higher the concentration of free ions. Under the action of the electric field of the electrode signal, a part of the ions will move to the electrode to form a noise voltage, which is called flow noise. Flow noise is more prominent when measuring low conductivity. The flow noise is related to the strength of the external electric field. The greater the induced signal at high flow rates, the greater the noise amplitude, and the output will be very unstable.
 
2. The rapid changes of fluid conductivity and pH value will also cause flow noise. The instability of the measurement performance of the upstream of the flowmeter is a typical example. The reason is that when different media are mixed unevenly, positive and negative ions are easily separated from the fluid. Under the action of the electrode signal electric field, some of the ions will move to the electrode, forming a flowing noise voltage and causing the output to be unstable.
 
3. Because the thickness of the laminar boundary layer of the high-velocity fluid close to the lining and the electrode becomes very thin, the roughness height of the lining and the electrode breaks through the thickness of the flow velocity laminar boundary layer, the fluid hits this part of the roughness height, and the flow velocity occurs. Divergence and mutation. A part of the flow velocity component that is the same (or opposite) to the central axis of the measuring tube is affected by the signal weight function, which has a great influence on the electrode signal and forms a large positive error, which is the high-end flow velocity noise.

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