Hysteresis measurements on straight bars and strips

The method of testing straight samples of high-permeability material, by using search-coils for the measurement of H and eliminating flux leakage from the length under test by means of compensating magnetizing windings, has been previously described in relation to permeability measurements. Its application to hysteresis measurements is found to involve more complicated switching operations, but a comparison of results obtained on bars and strips with those for rings of similar material shows good agreement when compensation is employed at each point on the loop. In the absence of compensation, large differences occur between the loops determined for straight and ring specimens. In tests on magnet-steel bars compensation produces a negligible effect on the results and is unnecessary. A drum controller to perform the switching operations required in carrying out a hysteresis loop under compensated conditions is described.