Error correction method for in-situ calibration of permanent magnet sodium flowmeter without bluff body based on low-frequency suppression

•The reason of large repeatability error is analyzed qualitatively.•Repeatability error is corrected by low-frequency suppression.•Three technical points are given to ensure correcting effect.•The specific steps are presented to correct repeatability and nonlinearity errors.•The accuracy of in-situ calibration is within ±3.0% through error corrections. In order to realize the in-situ calibration of the large-diameter permanent magnet sodium flowmeter without bluff body based on the cross-correlation method, its serious nonlinearity error must be corrected, and the reduction of the repeatability error is the prerequisite. The analysis shows that the velocity fluctuations near the sidewall are greater than the center, and the signal of low-frequency mainly comes from the sidewall, so the low-frequency signal will cause a large repeatability error of whole. Accordingly, an error correction method based on low-frequency suppression is proposed, and its technical points of the selection of signal electrodes, the filtration of fixed interference and the median filtering are given. The nonlinearity error is corrected by the quadratic function model. The accuracy of in-situ calibration is within ±3.0%.