How to verify the electromagnetic flow meter of electronic measuring instrument

Abstract: How to verify the electromagnetic flow meter information of electronic measuring instruments is provided by excellent flow meter and flow meter manufacturers and quotation manufacturers. Since the electromagnetic flowmeter must be used continuously online, it is almost impossible to dismantle it and transport it to the National Metrology and Testing Center for verification. Therefore, it is necessary to verify the accuracy of the large-diameter electromagnetic flowmeter used in the field. Accuracy test of electromagnetic flowmeter. More flowmeter manufacturers choose models and price quotations. You are welcome to inquire. The following is the details of the article on how to verify electromagnetic flowmeters for electronic measuring instruments. Since the electromagnetic flowmeter must be used continuously online, it is almost impossible to dismantle it and transport it to the National Metrology and Testing Center for verification. Therefore, it is necessary to verify the accuracy of the large-diameter electromagnetic flowmeter used in the field. The accuracy verification of electromagnetic flowmeter is also very useful for the management of electromagnetic flowmeter, to ensure its accuracy and reliability, to accumulate original comparison data, and to do future verification and verification. The accuracy verification of the electromagnetic flowmeter can use the volume of the clean water tank and the electromagnetic flowmeter to verify the equipment. Comprehensively verify the accuracy of the electromagnetic flowmeter to determine the accuracy of the electromagnetic flowmeter in the application process of the water plant, to ensure the authenticity of the measurement data or whether to replace the electromagnetic flowmeter. 1. Using the visual inspection method and the instrument method, use the GS8 to check whether the resistance value of the excitation coil of the sensor, the insulation resistance between the signal lines, the grounding resistance and other items meet the standards before leaving the factory, and whether the zero point and output current of the electromagnetic flowmeter converter meet the requirements. precision requirements. The specific detection method is as follows: (1) Measure the resistance value of the excitation coil to determine whether the excitation coil has an inter-turn short circuit (measure the resistance value between wire numbers 7 and 8), and the resistance value should be between 30 ohms and 170 ohms. If the resistance is the same as the factory record, the coil is considered to be good, and the magnetic field strength of the electromagnetic flowmeter sensor has not changed. (2) Measure the insulation resistance of the excitation coil to the ground (measurement line number 1 and 7 or 8) to judge whether the sensor is damp, and the resistance value should be greater than 20 megohms. (3) Measure the contact resistance between the electrode and the liquid (measurement line numbers 1 and 2 and 1 and 3), and indirectly evaluate the general condition of the surface of the electrode and the lining layer. For example, whether the electrode surface and the lining layer are attached to the deposition layer, and whether the deposition layer is conductive or insulating. The resistance value between them should be between 1 kohm and 1 megohm, and the resistance values ​​of wire numbers 1 and 2 and 1 and 3 should be roughly symmetrical. (4) Close the valve on the pipeline and check the zero point of the whole machine when the electromagnetic flowmeter is filled with liquid and the liquid does not flow. Make appropriate adjustments as appropriate. (5) Check the insulation resistance of each core wire of the signal cable and excitation cable, and check whether the shielding layer is in good condition. (6) Use the GS8 calibration instrument to test the output current of the converter. When given zero flow, the output current should be: 4.00mA; when given 100% flow, the output current should be: 20.00mA. The error of the output current value should be better than 1.5%. (7) Test the excitation current value (between terminals 7 and 8 of the converter), the positive and negative values ​​of the excitation current should be within the specified range, roughly 137 (5%) mA. Evaluate the influence of the external environment of the electromagnetic flowmeter on it, such as the excitation line and the signal line are laid in the same pipeline, the excitation line and the signal line are parallel to the high-voltage cable, and there are large transformers or motors around the influence on the operation accuracy of the electromagnetic flowmeter. , This evaluation mainly uses the visual method to observe whether the electromagnetic flowmeter in operation has sudden changes or fluctuations to roughly judge whether the electromagnetic flowmeter is disturbed by electromagnetic waves or other stray waves or whether there are air bubbles in the pipeline. Instruments and tools required for the verification of the electromagnetic flowmeter itself: one GS8, one 4-1/2 multimeter, one 500V megohmmeter, one pointer multimeter and common tools. 2. Verification of clear water tank volume method: The verification of the measurement accuracy of the electromagnetic flowmeter of the factory water of the water plant adopts the clear water tank volume method, which is one of the methods often used by water supply enterprises. Under the condition that the geometric dimensions of the clean water pool are accurately measured and the operating errors are reduced, a high comparison reference can be obtained. The principle of the clear water pool volume method is: use a high-precision steel ruler to measure the actual space plane size of the clear water pool and the suction well, and accurately calculate the actual plane area of ​​the clear water pool and the suction well. First, adjust the water level of the clear water pool to a higher water level and close all water outlet valves. After the water level of the clean water pool is stable, use the clean water pool level transmitter and manually measure the water level of the clean water pool and the suction well with a high-precision steel ruler. In order to correct the error caused by the leakage of valves such as clear water pool, measure the water level of clear water pool and suction well again after a certain interval, and calculate the amount of water leakage per unit time in order to correct the water metering and reduce errors. The purpose of recording the cumulative flow of the electromagnetic flowmeter to be verified, and manually measuring the liquid level of the clean water pool and suction well is to verify the accuracy of the liquid level transmitter. Then turn on the water pump, open the water outlet valve, and after a certain period of time, close the water outlet valve to stop the pump. When the water level in the clear water pool is stable,Use the clear water tank level transmitter again and use a high-precision steel ruler to manually and accurately measure the water level of the clear water tank and the suction well, record the water level of the clear water tank and the suction well again, and record the cumulative flow of the electromagnetic flowmeter to be verified.
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