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Five aspects of the routine inspection and inspection of electromagnetic flowmeter

The routine inspection of electromagnetic flowmeter usually includes electrode contact resistance, polarization voltage of the electrode, interference of signal cable, and determination of the presence or absence of ground potential and the flow of stray current in the pipeline. Here is a brief introduction for everyone:

I. Electrode contact resistance measurement The liquid contact resistance value of the electrode spoon can be measured, and the flow sensor can be removed from the pipeline to indirectly estimate the general condition of the surface of the juice electrode and the lining layer, which is helpful for analyzing the cause of the failure.

Second, the polarization voltage of the electrode to measure the polarization voltage between the electrode and the liquid will help to determine whether the zero point instability or output sloshing fault is caused by the contamination or coverage of the electrode. Use the digital multimeter 2V DC file to measure the polarization voltage between the two electrodes and the ground separately (the electromagnetic flowmeter can be tested without stopping the power, or it can be stopped). If the two measurements are nearly equal, the electrode is not contaminated or covered, otherwise the electrode is contaminated or covered. The magnitude of the polarization voltage is determined by the electrode material; the electrode potential and the nature of the liquid. The measured value may be between a few mV and several hundred mV. Since the contamination of the two electrodes in operation is not exactly the same symmetry, the voltage across the electrodes forms an asymmetric common mode voltage. The asymmetrical common mode voltage becomes a differential mode signal, causing a zero offset.

Third, the signal cable interference measurement signal cable by the external static induction and electromagnetic induction interference will make the electromagnetic flowmeter zero point change. In order to determine whether the zero point change is affected by the signal cable interference potential, it is necessary to determine the general extent of the interference and the degree of influence on the electromagnetic flowmeter.

Fourth, determine the presence or absence of ground potential electromagnetic flow juice during normal use, such as the state of the electric (force) machine near the sensor (such as leakage), the ground potential will change and cause zero point changes. Check if there is any influence in this way. Short-circuit the converter working ground C terminal and the protective ground G terminal, and judge whether there is a ground potential by zero point (or indication value).

V. Pipeline stray current flow direction discrimination Sometimes the interference source for finding pipeline spurs is still downstream in the upstream of the flow sensor to narrow the search range and try to reduce or eliminate the influence of stray current interference.

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