Obtaining the d.c. properties of soft magnetic materials using an open circuit measurement technique.

Hysteresis curves have been obtained for non-oriented electrical steel in strip geometry using an open circuit as the distance from the surface of the strip to the Hall probe is increased. An additional study looked at the influence of the solenoid length on the measured properties. Measurement of the hysteresis curves at several finite distances has allowed extrapolation to the surface field and hence also the actual field since the tangential component of H is continuous across a boundary. Some discrepancy between open circuit and closed circuit measurement is seen in the value of coercivity and is believed to be due to different magnetisation processes occurring in an open circuit due to the presence of an extra magnetostatic energy contribution associated with the demagnetising field.