How to avoid the electrode surface effect of the electromagnetic flowmeter the so-called electrode surface effect refers to the electrode surface chemical reaction effect, electrochemical phenomenon, polarization potential and the catalytic effect of the electrode from four aspects:

1. Chemical reaction effect: it refers to the passive film or oxidation layer formed on the electrode surface after contact between the electrode and the measured medium. At this time, the electrode was not corroded, but the passive film or oxidation layer formed increased the contact resistance of the electrode surface.

Tantalum and water tantalum is corrosion-resistant to water. If tantalum electrode is chosen to measure water flow, it is wrong.

2. Electrochemical phenomenon: it refers to the potential change on the electrode surface when the electrode is in contact with the measured medium.For example, when measuring the fluid flow of solid particles containing sand or fiber slurry, the solid particles graze the electrode. Although the electrode is not corroded, the electrode is suddenly changed by the contact potential of the impact surface, which makes the output signal of the meter appear peak pulse to form interference.

3. Polarization potential: it refers to the polarity difference of electrode-induced electromotive force between the two electrodes, resulting in polarization of electrolyte on the electrode surface.In the early days, the electromagnetic flowmeter used dc excitation electrode to have a serious polarization phenomenon, but now it USES low-frequency square wave excitation. Low-frequency rectangular wave excitation combines the advantages of dc excitation and ac excitation. Although alternating excitation weakens the polarization potential by several orders of magnitude, it cannot completely eliminate the influence of polarization potential interference.

4. Catalytic action: it refers to the chemical reaction of the measured medium under the action of electrode, which affects the measurement.For example, when the platinum electrode electromagnetic flowmeter is measuring hydrogen peroxide, although the platinum electrode is not corroded, hydrogen peroxide will generate vapor on the surface of the electrode, blocking the electrical path and causing fluctuations in the output signal.

Example: platinum and platinum hydrogen peroxide are corrosion-resistant to hydrogen peroxide. If platinum electrode is chosen to measure the flow rate of hydrogen peroxide, it is wrong. This is because when measuring hydrogen peroxide at low pressure (0.3mpa), the electrical path of vapor resistance resistance on the electrode surface will affect the measurement.

Therefore, the electromagnetic flowmeter selection on the electrode is very important, there is a need to welcome you to consult!We'll be at your service.