GB875710A - Magnetic susceptibility measuring instrument - Google Patents

Abstract

875,710. Magnetic tests. NATIONAL RESEARCH DEVELOPMENT CORPORATION. April 14, 1959 [April 14, 1958], No. 11756/58. Class 37. The magnetic susceptibility of a specimen is determined by inserting it in an air gap of a magnetic network which is energized with a magnetic flux source so that two points in the network have equal magnetic potential, the two points are joined by a magnetic link which contains a sensitive detector of magnetic flux. The magnetic susceptibility meter shown in Fig. 1 comprises a permanent magnet ABC in conjunction with which a soft iron bar D, E, F forms air gaps X, Y. The reluctance of gap Y is adjusted until no flux passes through the flux detector G, for example by moving a ferromagnetic body in the vicinity of gap Y or by altering the reluctance of the arm D, E by withdrawing or inserting iron screws. The specimen to be measured is then inserted into gap X so that flux passes through the detector G which measures the change. The detector may be an indium antimonide Hall effect element driven by a transistor oscillator with the Hall voltage amplified by a transistor amplifier. In the modification shown in Fig. 2, the permanent magnet ABC is associated with the detector G and four air gaps into any of which the specimen may be inserted. In a modification shown in Fig. 3, the flux produced from the magnet ABC is opposed by an equal flux produced by the winding H so that no flux passes through detector G. In a further embodiment shown in the Figure accompanying the Complete Specification two electromagnets having windings B and H are used, the fluxes being in opposition so that the detector G gives zero or a fixed datum output which changes when the specimen to be tested is inserted in either gap X or Y.