GB725188A - Improvements in and relating to methods of and devices for determining the magnetic properties of specimens of magnetic material - Google Patents

Abstract

725,188. Electrical tests. GENERAL ELECTRIC CO. March 23, 1953 [March 26, 1952], No. 7914/53. Class 37. In a method of measuring magnetic properties of magnetic materials by magnetizing a specimen with a time-varying flux having a component parallel to the surface of the specimen, the voltage V1 along the surface of the specimen in a direction perpendicular to the direction of the flux component is applied via pointed conductors 16, 17 to a measuring instrument of high input impedance to give a reading representative of the rate of change of flux through the cross-section measured. The testing apparatus, Fig. 5, includes a pair of laminated legs 23, 24, bent over to form an air gap and carrying a coil 27, in which a voltage V2 representative of the time-rate of change of intensity in the specimen is induced. The voltages may be applied to a wattmeter via amplifier circuit arrangements, Fig. 4 (not shown), wherein the amplifier for the voltage V2 includes an integrating circuit so that the power loss due to hysteresis, J HdB, may be indicated. In a modified application of the apparatus, Fig. 5, the specimen 19 is magnetized by applying a generator 86, Fig. 6, to the coil 27 and in this case the coil current is representative of the field intensity H. In this case, however, the reluctance of the arms is more critical and the application is limited tc measuring relative power losses. An arrange. ment for displaying the hysteresis loop by applying the two voltages, after integration, to the horizontal and vertical plates of an oscilloscope is described with reference to Fig. 7 (not shown) and in a further arrangement, Fig. 8, the integrated outputs of amplifiers 94, 99 are rectified in rectifiers 100, 101, and supplied to a ratio instrument 102 which, by giving a reading proportional to the quotient of the outputs from rectifier 100 and rectifier 101, provides a measure of the permeability of the specimen. Switches 105, 106, controlling the insertion of condensers 103, 104 enable either peak or average readings to be made.