A 60-Cycle Hysteresis Loop Tracer for small Samples of Low-Permeability Material

The basic components of this instrument are (a). A large (35-pound) exciting coil with a pickup coil at its center. (b). An amplifier and integrating circuit. (c). A cathode-ray oscillograph. The instrument provides a convenient and rapid means of determining the magnetic properties of samples much smaller than can be used conveniently with the ballistic method. Absolute calibration provides greater accuracy and reliability than has been obtained previously in this type of apparatus. Phase errors are reduced to low values through the use of a compensated integrating network with absolute means of adjustment. This network provides a much higher output voltage than the usual circuit and thus makes practicable operation at the power line frequency and the consequent use of an exciting coil of sufficient size to minimize end effect errors and to allow operation at fields as high as 1,000 oersteds for long periods of time.