Talk about the five special inspections of electromagnetic flowmeter
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1. Electrode contact resistance. Measuring the liquid contact resistance value of the electrode spoon can indirectly evaluate the general condition of the surface of the electrode and the liner layer without removing the flow sensor from the pipe, which is helpful for analyzing the cause of the failure.
2. Polarization voltage of the electrode. Measuring the polarization voltage between the electrode and the liquid will help determine if the zero-point instability or output sloshing fault is caused by the electrode being contaminated or covered. With a digital multimeter 2V DC gear, measure the polarization voltage between the two electrodes and the ground (the electromagnetic flowmeter can be measured without interruption or blackout). If the two measurements are nearly equal, the electrodes are not contaminated or covered. The magnitude of the polarization voltage is determined by the "electrode potential" of the electrode material and the nature of the liquid. The measured value may be between a few mV and a few hundred mV. Because the two electrodes are actually contaminated during operation, it is not possible to be completely symmetrical, so the voltage across the two electrodes forms an asymmetric common-mode voltage. The asymmetric common-mode voltage becomes a differential mode signal, causing a zero offset.
3. Pipeline stray current flow discriminant. Sometimes to find the spurious source of interference in the pipeline upstream or downstream of the flow sensor to narrow the search, try to reduce or eliminate the effects of stray current interference.
4. Determination of signal cable interference. The signal cable is affected by the external electrostatic induction and electromagnetic induction interference will make the electromagnetic flowmeter zero point change. To determine whether the zero point change is due to signal cable interference potential influences, it is necessary to determine the general scope of the interference and the degree of influence on the electromagnetic flowmeter.
5. Determine if there is a ground potential. Electromagnetic flow juice in the normal use of the process, such as the sensor near the motor (force) status changes (such as leakage), the ground potential will change and cause a zero point change. Check if there is any influence in this way. Short circuit the converter's working ground C terminal and protective grounding G terminal, and judge whether there is a grounding potential by changing the zero point (or indication value).
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