Online calibration method for electromagnetic flowmeters

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　At the time of manufacture, the accuracy of the electromagnetic flowmeter has already been calibrated using a calibration line. However, in actual use, due to factors such as environmental conditions, fluid properties, and malfunctions in the instrument itself such as damaged components, it is necessary to perform a regular on-site calibration of flow meters after long-term use. To ensure the accuracy and reliability of electromagnetic flowmeters after fault repair as well as during long-term use, the following online calibration methods are listed: 1. Conduct a safety insulation test on the excitation coil of the electromagnetic flowmeter; the value should be greater than 20 MΩ. 　　2. Perform a copper resistance test on the excitation coil of the electromagnetic flowmeter; it should be the same as the original factory value (under the same ambient temperature). 　　3. Test the resistance of the sensor electrodes of the electromagnetic flowmeter; if the resistance value is between 2 and 20 kF, and charging and discharging phenomena occur along with similar resistances for the two electrodes, it is considered acceptable. 　　4. Test the excitation current of the electromagnetic flowmeter converter, and observe its output compared to the original current value of the converter; the error should not exceed ±0.25 mA. 　　5. Test the analog output and frequency output of the electromagnetic flowmeter converter, observe their linear variation, and calculate the maximum linear error, which should not exceed ±0.5%.