Abstract:As an efficient, accurate and convenient flow measurement instrument, electromagnetic flowmeter is widely used in the measurement of conductive fluids such as industrial fluid measurement, oilfield drilling fluid measurement and blood measurement. Due to the influence of external disturbance and flow velocity distribution, the electromagnetic flowmeter still has the problem of low measurement accuracy in the process of flow measurement. Improving the structure of the electromagnetic flowmeter excitation coil is one of the important means to improve accuracy. In this paper, based on a new type of positive eight sides, the accuracy of electromagnetic flow measurement was improved with magnetic field coil. Firstly, based on the study of the optimization principle of the weight function, the theoretical model of the magnetic field of the regular octagonal coil was analyzed to obtain the optimization idea of the electromagnetic flowmeter based on the uniform magnetic field theory. Secondly, based on the finite element analysis software, a simulation model of the regular octagonal excitation coil electromagnetic flowmeter was established, and the optimal structural parameters of the regular octagonal excitation coil magnetic field distribution were determined. By comparing the weight function distribution of the circular and square coils under the same conditions, the advantages of the uniformity of the weight function distribution of the regular octagonal coil were proved. Finally, an experimental platform was built to verify the magnetic field test experiment and the fluid test experiment. The magnetic field test results showed that the magnetic induction intensity of the regular octagonal coil electromagnetic flowmeter can be maintained at the central area of the pipeline. About 2.063 mT, the overall magnetic induction intensity fluctuation range is within 0.11 mT, indicating that the regular octagonal coil magnetic field has good uniformity. The fluid test result showed that when the flow rate is 0.743~2.582 m/s, the single-point relative indication value The maximum error is only 0.950%, and the system repeatability error is below 1.034%. The optimized system improves the measurement accuracy, which has guiding significance for the subsequent design of the excitation coil of the electromagnetic flow meter.