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1. What is the coil voltage included in the electromagnetic flow? The excitation coil voltage of an electromagnetic flowmeter is usually in the range of 5-50V, and the specific value depends on the instrument model, caliber size, and manufacturer design. 1. The working voltage of the excitation coil of electromagnetic flow meters with different diameters and models varies in common voltage ranges: - Small caliber instruments (DN10-DN50): commonly used 5-15V low-voltage excitation - Medium and large caliber instruments (DN65-DN1200) are lacking: mostly use 15-30V standard voltage - Extra large caliber or special applications (DN1400 or above): may require a higher voltage of 30-50V. 2. Influencing factors The specific value of excitation voltage is mainly affected by three factors: • Measuring tube diameter: the larger the diameter, the higher the required magnetic field strength, and the corresponding voltage increase. • Excitation methods: DC excitation, power frequency excitation, low-frequency rectangular wave excitation, etc. Different voltage requirements vary. • Manufacturer design: There are differences in technical solutions and component specifications adopted by different brands. 3 Practical application tips for installation and maintenance: - It is strictly prohibited to directly measure the excitation coil voltage on site, as it may damage the instrument electrical cleaning subunit. - It is necessary to consult the product manual of the corresponding model to obtain accurate parameters (such as the rated excitation voltage of the Yokogawa AXF series is 24V ± 10%, and the Cologne IFC300 series is 22.5V). - The coil resistance value is usually 20-200 Ω (at 25 ℃), and the coil state can be indirectly judged 
2. Online calibration method for electromagnetic flowmeter
The online calibration method for electromagnetic flowmeter mainly includes the following process: safety insulation test of excitation coil. Use a megohmmeter to test the insulation resistance of the excitation coil of the electromagnetic flowmeter to ensure that its insulation performance meets the requirements.
. The test result should be greater than 20M Ω to verify the good insulation state between the coil and the shell, and to avoid measurement errors or equipment damage caused by insulation failure. The resistance of the sensor electrode to ground is measured using a multimeter or specialized tester. If the resistance value is between 2k Ω and 20k Ω, and there is charging and discharging phenomenon during the testing process (such as slow drop after pointer swing), and the resistance values of the two electrodes are similar, it indicates that the electrode state is normal. This test can determine whether the electrode is contaminated or covered with insulation layer, ensuring the accuracy of signal acquisition. The linearity test of the converter output signal tests the analog output (such as 4-20mA current) and frequency output of the converter. A known flow signal is input through a standard signal source, and the linear variation of the output value is observed. Calculate the maximum linear error, which should not exceed ± 0.5%, to verify whether the conversion accuracy of the converter for flow signals meets
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