This part of IEC 60404 is applicable to grain-oriented electrical steel strip and sheet specified in IEC 60404-8-7 for the measurement of magnetostriction characteristics under an applied AC magnetic field at 50 Hz or 60Hz. This document defines the general principles and technical details of the measurement of magnetostriction characteristics of grain-oriented electrical steel strip and sheet by means of a single sheet tester and an optical sensor. NOTE 1 The accelerometer method [5] is also an established method for the measurement of magnetostriction. However, it is more suited to the measurement of magnetostriction under an externally applied tensile or compressive stress, not zero stress, because it places a weight on the test specimen to prevent a deformation of the test specimen. Since this document includes the measurement at zero stress, the optical sensor method is provided as the optimum method. This document is applicable to the measurement of: the butterfly loop; the peak-to-peak value »p-p; the zero-to-peak value »0-p. The magnetostriction characteristics are determined for a sinusoidal induced secondary voltage, for a specified peak value of the magnetic polarization and at a specified magnetizing frequency. NOTE 2 Throughout this document the term magnetic polarization is used as described in IEC 60050-121-11-54. In some standards of the 60404 series, the term magnetic flux density is used.