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How to address the noise issues associated with insert-type electromagnetic flowmeters? The working principle of these flowmeters is based on Faraday’s law of electromagnetic induction; they determine the flow rate of the fluid by measuring the induced electromotive force in a conductive fluid within a magnetic field. The excitation magnetic field, the electrodes for detecting the induced electromotive force, the signal operational amplification circuit, and the analog-to-digital converter are all susceptible to coupling caused by electric and magnetic fields present in the operating environment. Therefore, electromagnetic coupling is the main source of interference in flow measurement. Additionally, the electrochemical reactions of the liquid being measured and mud interference represent other sources of noise in flow measurement. The mechanism of differential interference and countermeasures, as well as the mechanism of noise generation in insert-type electromagnetic flowmeters and the corresponding countermeasures: In current designs of electromagnetic flowmeters, the low-frequency rectangular wave excitation method combines the advantages of both direct current excitation and alternating current excitation, making it one of the main excitation methods for insert-type electromagnetic flowmeters. Under low-frequency excitation, its interference is mainly manifested as differential interference signals generated by sudden changes in the excitation current. The excitation magnetic field signal of plug-in electromagnetic flowmeters is a low-frequency rectangular wave; in fact, as the excitation current changes (dI/dt), a differential interference signal is generated in the magnetic field. As the current stabilizes, this interference signal disappears, and therefore synchronous sampling technology can effectively suppress the differential interference signal. In actual design, the analog-to-digital converter uses AD Company’s 24-bit Sigma Delta analog-to-digital converter, the AD7714. The AD7714 allows control of the sampling start time via both hardware and software methods, thereby enabling synchronized sampling. When using software control, the analog-to-digital converter is in a reset state when the FSYNC bit in the control register is at logic 1; writing logic 0 to this bit causes the device to start sampling the input signal. In the application, the low-frequency excitation signal is generated by the internal timer of the MSP430 microcontroller, which simultaneously generates the sampling signal. The sampling start time is delayed by 14 cycles of the excitation signal. Mechanism and countermeasures for power-frequency series mode interference: In the working environment of insert-type electromagnetic flowmeters, there are numerous power-frequency signals present. The power-frequency interference noise generated in the excitation circuit, electrodes, and front-end amplifiers has a significant impact on the accurate measurement of flow rate. Among them, the power-frequency radiation magnetic field (including its harmonics) that is coupled into the excitation circuit causes fluctuations in the excitation magnetic field, affecting flow measurement. For more information, please visit the company’s official website at http://www.yb1518.com/. Please retain this link when reproducing the content! http://www.yb1518.com/UploadFiles/201412269333291.jpg