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Electromagnetic flowmeter zero instability how to correct the introduction

Electromagnetic flowmeter is one of the most commonly used flowmeters in industrial metering. Because electromagnetic flowmeter has the influence of fluid density, viscosity, temperature, pressure and conductivity modification, the converter adopts novel excitation method and has low power consumption. The zero point is stable and the accuracy is high. The traffic planning degree can reach 150:1, and so on, but the application will have disadvantages.

Five inspection cleaning methods for electromagnetic flowmeter zero point instability.

First, first clean the inspection: check the program to check the zero point The electromagnetic flowmeter is not stable. First, according to the process, consider the beginning of the query and discriminate, and then carefully check and test the defects. The order of the inspection items listed in the process is:
(1) It can be inquired or inquired to know that there is no need for a large operation, that is, it is difficult to make it easy;
(2) According to the previous on-site repair experience, the frequency of occurrence is higher and the probability of occurrence may be higher in the future;
(3) Check the sequential needs required by itself. If you start the inquiry to confirm the reasons for the shortcomings of the team, you can also do a detailed check in advance.

Second, the electromagnetic flowmeter sensor is not perfect according to the ground, such as stray current and other external annoyance:
The external disturbances such as the stray current of the pipeline affect the excellent grounding protection of the primary electromagnetic flowmeter. Generally, the grounding resistance is less than 1000. Do not share the grounding with the motor. Sometimes the environmental conditions are good, the electromagnetic flowmeter can be operated normally without grounding, but once the excellent environment does not exist, there will be shortcomings on the surface, and then checking again will cause more troubles.
Changes in the condition of the power equipment adjacent to the flow sensor (such as increased leakage current) constitute a change in ground potential, which causes the electromagnetic flowmeter to change at zero.

Third, the electromagnetic flowmeter liquid (such as liquid conductivity uniformity, electrode contamination and other reasons); liquid conductivity changes or uneven, will stop the zero point when stopped, the output will shake the activity. Therefore, the flowmeter orientation should be kept away from the written chemical solution point or the chemical reaction section of the pipeline, and the flow sensor is optimally installed upstream of these places.
If the liquid contains a solid phase, or the impurities accumulate on the inner wall of the measuring tube, or the scale on the inner wall of the measuring tube, or the electrode is contaminated by grease, etc., there may be a slight change. Because the surface fouling of the inner wall surface and the degree of contamination of the electrode may not be exactly the same and symmetrical, the equilibrium of the plant's initial withering setting is damaged. The lively method removes the dirt and deposits the scale layer; if the change of the zero group is not large, the zero adjustment can be checked from the beginning.

Fourth, the electromagnetic flowmeter signal loop insulation decreases.
A drop in the insulation of the signal loop can constitute a zero point instability. The soil of the signal loop insulation is caused by the foot and the insulation of the pole portion is lowered, but the insulation of the signal cable and its terminals cannot be cleaned or damaged. Because sometimes the site environment is very strict, slightly ignore the surface cover / wire joints sealed carelessly, filled with moisture mist or dusty dust invading the surface junction box or cable protection layer, so that the insulation is lowered. The signal loop insulation resistance check is carried out according to the two side points of the cable side and the flow sensor side, and is checked by a megohmmeter. It can be done first because the signal cable is simple. The flow sensor is divided into two parts: the liquid is connected to the surface of the electrode to measure the contact resistance and the tube is measured, and the U-pole insulation resistance.

5. Check the electrode contact resistance and the electrode insulation resistance in two steps.
(1) Fully liquid measuring electrode surface spoon liquid contact resistance flow sensor to remove the signal cable wiring, use a multimeter to measure the resistance of each electrode and the connection address, the voltage between the two electrodes to the ground should be 10%-20 %. The measurement of "one/electrode contact resistance" in Section 9 will be further clarified.
(2) Empty tube measurement electrode insulation Empty the measuring tube and dry it on the inner surface. After it is completely monotonous, measure the resistance between each electrode and ground with H500VDC megger. The resistance must be above 100MΩ.

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