Nowadays, electromagnetic flowmeters have been widely used, but in order to make them better used, we cannot ignore its detection.
Nowadays, electromagnetic flowmeters have been widely used, but in order to make them better used, we cannot ignore its detection. Below we will talk about five special tests for electromagnetic flowmeters.
1. Electrode contact resistance.
Measuring the liquid contact resistance value of the electrode scoop can indirectly evaluate the general condition of the electrode and lining surface without removing the flow sensor from the pipeline, which is helpful to analyze the cause of the failure.
2. The polarization voltage of the electrode.
Measuring the polarization voltage between the electrode and the liquid will help determine whether the zero point instability or output shaking failure is caused by the electrode being contaminated or covered. Use the 2V DC range of a digital multimeter to measure the polarization voltage between the two electrodes and the ground (the electromagnetic flowmeter can be measured without power outage or without power outage). If the two measurements are nearly equal, the electrode is not contaminated or covered. The size of the polarization voltage depends on the "electrode potential" of the electrode material and the properties of the liquid. The measured value may range from a few mV to hundreds of mV. Because in fact, the contamination conditions of the two electrodes during operation cannot be the same and symmetrical, so the voltages on the two electrodes form an asymmetric common mode voltage. The asymmetric common mode voltage becomes a differential mode signal, causing a zero offset.
3. Identification of pipeline stray current flow direction.
Sometimes, in order to find whether the source of stray interference in the pipeline is upstream or downstream of the flow sensor, we can narrow the search range and try to reduce or eliminate the influence of stray current interference.
4. Determination of signal cable interference.
The signal cable is interfered by external electrostatic induction and electromagnetic induction, which will cause the zero point of the electromagnetic flowmeter to change. In order to determine whether the zero point change is due to the interference potential of the signal cable, it is necessary to determine the general scope of the interference and the degree of impact on the electromagnetic flowmeter.
5. Determine whether there is ground potential.
During normal use of electromagnetic flow juice, if the motor (force) state near the sensor changes (such as leakage), the ground potential will change and cause the zero point to change. To check whether this is affected, you can short-circuit the converter's working ground C terminal and protective ground G terminal, and use the zero point (or indicated value) change to determine whether there is a ground potential.
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