GB645902A - Improvements in metal detection or inspection devices and the like - Google Patents

Abstract

645,902. Magnetic and electric tests. RADIO CORPORATION OF AMERICA. April 1, 1948, Nos. 9246 and 9247. Convention dates, April 19, 1947, and Feb. 3, 1948. [Class 37] The invention relates to apparatus for locating magnetic or conducting materials comprising two magnetically-coupled circuits, normally not mutually inductive, whose balance condition is upset by the presence of the magnetic or conducting material, and consists of means for neutralizing stray voltages in the coil systems by coupling the primary and secondary windings through two cores whose magnetic properties are such as to give induced voltages in quadrature, so that the rectangular components of any unrequired unbalance voltage may be balanced out independently. The secondary, or, as shown (Fig. 1c), the primary, may consist of two similar opposed windings 15, 17 connected in parallel or in series. Two adjustable metal slugs 49, 51, Figs. 6, 7, are introduced between the primaries 15, 17 and the secondary 19, consisting of such metals as to induce voltages, in quadrature into the secondary, the magnitude of such voltages being adjusted by knobs 41, 47 through worms 37, 43 and gear-wheels 33, 35, altering the position of each slug with respect to the coils. A fabric belt 31 between the primary and secondary windings carries the articles to be inspected. A list of metals and their properties (Fig. 8, not shown) enables appropriate choice of metals for the slugs to be made.