GB624083A - Improvements in or relating to magnetic azimuthal direction-indicating apparatus - Google Patents

Abstract

624,083. Earth inductor compasses. HINE, A., and HITCHINS, H. L. March 12, 1946, No. 7764. [Class 37] [Also in Group XX] A magnetic compass provided with means for generating a magnetic field or fields to neutralize the effects of the vertical component of the earth's magnetic field is characterised in that the intensity of the neutralizing field or fields is controlled by the output of a normally vertical saturable inductor detector element. In the saturable inductor shown, Fig. 1, installed, for example, in an aircraft, the required compensating field is derived from an energized coil c gimballed and weighted so that it is maintained horizontal and freely surrounding two detector elements a, b fixedly mounted fore and aft and athwartships respectively. A third vertical detector f secured to the craft develops an output E.M.F. responsively to the influence of the vertical component of the earth's magnetic field and this is applied as shown, Fig. 2, through an amplifier-rectifier g to energize the coil c; the output from g is preferably fed back through an additional winding on the detector f in series with the coil c. The current through the coil c as it is the result of an E.M.F. generated in detector f varies automatically as the detector E.M.F. changes with change in terrestrial position of the compass. The detector f may be arranged to swing freely with the gimballed coil c. In a modification, Fig. 5 (not shown), the compensation is effected by means of coils wound directly on the detectors a, b and connected respectively to separate sine potentiometers fed by the circuit f, g and co-operating with a gimballed vertical gyro or a gimballed pendulum, Figs. 3 and 4 (not shown). As applied in a saturable inductor, Fig. 6, having a single rotary detector o maintained constantly E-W, the compensating field is produced by fixed radial coils p<SP>1</SP>, p<SP>2</SP>, q<SP>1</SP>, q<SP>2</SP> with sine potentiometer gyroscope control similarly to Figs. 4 and 5. The radial coils may be omitted and a single neutralizing coil wound directly on the E-W detector, Fig. 7 (not shown), and supplied with current from a sine potentiometer controlled by the E-W tilting gimbal element of a pendulum or vertical gyro, the actuating gimbal axis of which is maintained constantly N-S. Three or more detectors may be suitably arranged to supersede the pair of detectors a, b of Fig. 1 and the single detector o in Fig. 6 or a gimballed neutralizing coil c as in Fig. 1 may surround the single detector o. Drawings accompanying the Provisional Specification, Figs. 1 and 2 (not shown), illustrate the enclosure of a construction similar to Fig. 1 in a bowl containing an oscillationdamping liquid.