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A newly developed measurement system was comprehensively tested for the industrially attractive case of an open magnetic circuit. Series of industrial electrical steels were magnetized by a single yoke through a gap of several millimeters. According to standards, the magnetic induction waveform was adjusted to a 50-Hz sine curve using a digital feedback procedure. The magnetic surface fields above the sample were measured directly by a vertically mounted array of three Hall sensors. The actual magnetic field was determined by a linear extrapolation of the measured field profile to the sample face. It was experimentally shown that control of the induction waveform and simultaneous direct determination of the sample field make the hysteresis loop measurements independent of the yoke-sample gap. In addition, the obtained physically correct data show good linear correlations with the corresponding standard values measured by a single sheet tester. These outcomes are important for revision of the principles of industrial testing and further development of the measurement standards.