Ensuring the accuracy of electromagnetic flowmeters during application has always been a key concern for users. In the past, calibration of electromagnetic flowmeters required sending them to specialized calibration equipment. However, with the development of electromagnetic flowmeter manufacturing technology and the expansion of application industries, the use of electromagnetic flowmeters is increasing, and their diameters are becoming larger, making it increasingly difficult to send them back to calibration equipment for verification. Especially in the water supply industry, due to the large pipe diameters and industry characteristics, performing flow interruption and meter removal for external calibration is extremely difficult, time-consuming, labor-intensive, and sometimes impossible. However, according to the requirements of the ISO 9001 quality management system, electromagnetic flowmeters, as metering instruments, need to undergo periodic inspection. Therefore, users and manufacturers of electromagnetic flowmeters have been searching for an online inspection method to replace the traditional offline calibration method. Online Inspection Methods for Electromagnetic Flowmeters Commonly Used Domestically and Internationally in Recent Years: Online Calibration Methods for Large-Diameter Electromagnetic Flowmeters In the 1990s, the Shanghai water system began exploring online inspection and verification. They used dedicated analog signal generators to test the converter, and sensor inspection involved indirect methods such as testing electrode liquid contact resistance, checking the insulation resistance and copper resistance of the excitation coil, including the excitation connection cable, and checking the excitation current output by the converter, as well as verifying the magnetic field strength. In pipelines with flow cessation conditions, the sensor was accessed through a pre-installed manhole near the sensor to check for dirt and deposits on the electrodes and lining, and then cleaned. With the cooperation of the electromagnetic flowmeter manufacturer, the Shanghai Water Supply Company and Raw Water Company explored and accumulated inspection experience with over 300 large-diameter electromagnetic flowmeters, and drafted the "Online Calibration Methods for Large-Diameter Electromagnetic Flowmeters" between 1997 and 1998, which was piloted in enterprises under the Shanghai Municipal Public Utilities Bureau. Currently, the Shanghai Water Authority is developing the local industry standard "Online Calibration Specifications for Electromagnetic Flowmeters" based on this document. The same concept is mentioned in some literature, such as the on-site testing methods for electromagnetic flowmeters used by the Tokyo Metropolitan Waterworks Bureau and Mitsubishi Chemical Industries. The GS9 online electromagnetic flowmeter calibrator is the most widely used in Europe, and its online testing technology is the most mature. Some major electromagnetic flowmeter manufacturers have also developed dedicated online testing instruments based on the above methods, such as KROHNE's GS9 online electromagnetic flowmeter calibrator. This instrument is a comprehensive calibrator for testing electromagnetic flowmeter sensors and converters. Its testing includes electrode signals, analog flow output measurement, on-site excitation current measurement, current and frequency output measurement, coil and electrode resistance, etc., and records the data, which can also be transmitted to a PC. The GS9's testing process is very simple: just connect the flowmeter according to the cable markings (plug and play), then start the automatic calibration. The data is stored in the internal memory (70 meters), and can then be transferred to a computer for processing. The testing instrument automatically loads the settings for the instrument's GK, range, diameter, excitation current, current, and frequency output, and begins measuring the excitation current, detecting coil and electrode resistance (short circuit or open circuit), testing the signals of the two measuring electrodes, and testing the converter's current and frequency output. It provides "Pass" or "Fail" diagnoses for different components of the converter and stores the entire calibration process. The entire calibration process is automatically controlled, with calibration data uploaded to the computer via RS232 communication. Traceability: The GS9 is directly traceable to KROHNE's highest-end calibrator (GS100) and (Netherlands Institute of Metrology and Testing NMI). The sensor calibration uncertainty is 0.03%, and the GS9's measurement uncertainty is 0.09%. While connecting the GS9 to a PC via RS232 in the field or instrument room to complete the above online testing or using dedicated diagnostic instruments eliminates the need to stop the pipeline flow before testing the flowmeter, external testing equipment is still required to complete the entire testing process. Therefore, developing flowmeters with built-in diagnostic and testing functions is a current trend in flowmeter research and development. The IFC300 is an electromagnetic flowmeter with self-diagnostic capabilities, developed for the reasons mentioned above. It integrates all the functions of the online calibrator described earlier. When users need to calibrate the flowmeter, they can simply print the test results from a computer via HART or a bus interface. This new electromagnetic flowmeter is a state-of-the-art design conforming to the requirements of VDI-NAMUR-WIB 2650 guidelines. Compared to conventional electromagnetic flowmeter converters, this model adds many online diagnostic functions, such as: * Process parameters (conductivity, coil temperature, gases in the liquid, flow regime); * Environmental parameters (converter temperature, external magnetic field, and installation conditions). The widespread adoption of online calibration methods still requires time and industry approval. While the online calibration method for electromagnetic flowmeters is maturing from its inception to application, its nationwide adoption across various industries will take some time. The biggest challenge lies in the fact that, as a metering instrument, the online inspection standards for electromagnetic flowmeters require approval from the national technical supervision department and relevant industry associations. For the solutions and equipment mentioned above to gain nationwide acceptance, collaboration between electromagnetic flowmeter manufacturers, users, and relevant national departments is essential. We are pleased to see that in the Shanghai water system, where electromagnetic flowmeters are widely used, industry user organizations, in conjunction with technical supervision departments and manufacturers, have completed and implemented industry regulations for the online inspection and verification of large-diameter electromagnetic flowmeters. We hope that more industries and manufacturers will join this technical solution, ensuring that users of electromagnetic flowmeters have clear guidelines to follow.