| 摘要 |
A testing instrument for automatically non-destructively determining the hardened depth in accordance with the coercive force of a steel by periodically impressing a D.C. magnetic field externally on the steel by energizing an electromagnet from a D.C. source, measuring the magnetic flux density of said D.C. magnetic field by means of a Hall element while varying the magnetomotive force of said field, integrating the measured value of magnetic flux density, applying the integrated value to the electromagnet alternately with connection of the D.C. source to the electromagnet and reading the value of the magnetomotive force to said field at the point when the magnetic flux density has reached zero or a prescribed value.
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