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Introduction to the special detection method of electromagnetic flowmeter

Electromagnetic flowmeters are widely used in petroleum, chemical, metallurgy, textile, food, pharmaceutical, paper and other industries as well as environmental protection, municipal management, water conservancy construction and other fields. The main components of the sensor are: measuring tube, electrode, excitation coil, iron core and yoke housing. The product is mainly used to measure the volume flow in conductive liquids and slurries in closed pipes, including highly corrosive liquids such as acids, alkalis and salts.
Special detection method for electromagnetic flowmeter:
1. Determination of signal cable interference
The signal cable is subject to external static induction and electromagnetic induction interference, which causes the electromagnetic flowmeter to change at zero. 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.
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 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. The magnitude of the polarization voltage is determined by the "electrode potential" of the electrode material and the nature of the liquid, and the measured value may be between several 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.
3. Pipe flow stray current flow direction discrimination
Sometimes the source of interference for pipeline spurs is upstream or downstream of the flow sensor to narrow the search range and try to reduce or eliminate the effects of stray current interference.
4, electrode contact resistance
Measuring the liquid contact resistance of the electrode spoon can indirectly evaluate the general condition of the electrode and the backing layer without removing the flow sensor from the pipe, which is helpful for analyzing the cause of the failure.
5, determine the presence or absence of ground potential
During the normal use of the electromagnetic flow juice, if the motor (force) state changes (such as leakage) near the sensor, the ground potential will change and cause a zero point change. 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).

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