GB600165A - Improvements in magnetic compasses - Google Patents

Abstract

600,165. Compasses. SPERRY GYROSCOPE CO., Inc. Sept. 28, 1945, No. 25312. Convention date, Sept. 28, 1944. [Class 37] [Also in Group XXXVIII] A vertical rod or wire 1, Fig. 1, carries a varying or alternating current so that it vibrates in a plane normal to the horizontal component of the earth's magnetic field. Preferably, condenser plates 38, 39, Figs. 1, 4, pick up the components of vibration, and the induced voltages are applied to coils 42, 43, Fig. 4, to position rotor 45, or may be applied to the plates of a cathode-ray tube directly, and through phase-sensitive rectifiers to avoid 180 degrees ambiguity, Fig. 6 (not shown). Any component of the driving voltage in the pick-up circuits may be balanced out by adding adjustable voltages from potentiometers in parallel with the wire. The wire preferably vibrates at its resonant frequency and forms a condenser with cylinder 6 which is in the input of the multi-vibrator 26 controlling the oscillator 27 supplying the wire-current. The wire is preferably mounted in an evacuated envelope which is supported from gimbals to allow pendulous movement in any vertical plane, and its natural frequency is adjustable by screw 9 determining its tension. Vibration is started by discharging a condenser through coils 32 to produce a momentary magnetic field, Fig. 5 (not shown). The wire may consist of a quartz fibre with a metallic coating so as to have a very high Q value, when it will exhibit gyroscopic properties and tend to resist any variation of its plane of vibration.