GB399957A - Improvements in apparatus for determining the direction of magnetic or electro-magnetic fields - Google Patents

Abstract

399,957. Magnetic tests ; measuring phase-diferences; directive wireless signalling. SOC. INDUSTRIELLE DES PROCEDES W. A. LOTH, 20, Avenue Kleber, Paris. Aug..4, 1932, No. 21922. Convention date, Aug. 6, 1931. [Class 37.] The direction of emission of an electromagnetic or magnetic field is determined by employing two-receivers in the first of which the phase of the induced current remains unchanged whilst the current phase in the second is variable, means being provided for determining, by the known vectorial sum and difference method, a predetermined phase relationship between the currents in the receivers, together with means for modifying the position of the second receiver with respect to the transmitter. The apparatus may be employed on air- or water-craft for locating it in relation to an energized cable, the receiving aerials being combinations of open and frame aerials, or frame aerials horizontally and vertically disposed. In the general case, impedances Z<1>, Z<2> supply currents, which are the sum and difference of the phase-displaced currents in circuits A, B, to a differential ammeter AD through rectifiers R<1>, R<2>. The impedances may comprise transformers having two secondaries or one winding centrally tapped. Fig. 5 shows one form of a direction indicator, an open antenna A being connected to the mid-point of a frame aerial L, condensers C<1>, C<2> being provided for tuning the respective circuits. The condensers can be adjusted together if the circuits are balanced in other capacity and inductance effects. Thermionic detectors T<1>, T<2> are supplied with the sum and difference currents and their outputs may be connected to amplifiers and a central zero ammeter G.