GB1208369A - Improvements in/or relating to apparatus for measuring the angular separation between a determined direction and the direction of the earth's gravitational field - Google Patents

Abstract

1,208,369. Selective signalling. SOC. D' APPLICATIONS GENERALES D'ELECTRICITE ET DE MECANIQUE. 28 May, 1968 [31 May, 1967], No. 25402/68. Heading G4H. [Also in Division G1] Apparatus for measuring the angular separation α between an axis X-X, Fig. 8, representing a geological drilling line, and the earths gravitational field comprises a substantially point light source 13 adapted to emit, through a diaphragm 13a, pulses of light of a predetermined frequency along the axis X-X, a pendulum 3 mounted by means of a universal joint 4 on a shaft 5 rotated at a predetermined speed by a motor 10 to thus rotate the pendulum, the pendulum having a part-spherical analysis surface 6 moving in front of the light source 13, the surface 6 having two zones, Fig. 5, one of which is transparent and the other opaque, the shape of the transparent zone being such that the time during which light pulses emitted by the source 13 pass through this zone is dependent on the angle α, a photocell 9 disposed on the axis X-X to receive light pulses passing through the surface 6, the number of light pulses received by the photocell 9 during each rotation of the pendulum 3 being a direct measure of the required angle α. The motor 10 simultaneously drives the shaft 5 and a contact breaker 11 which in the circuit of the light source 13, thus providing a known number of light pulses for each revolution of the pendulum 3, so that the number of pulses transmitted by the transparent zone of the surface 6 during each revolution is dependent on the angle α. The pendulum is provided with an annular mass 23 and the apparatus may be contained in a liquid-filled casing providing damping for the movement of the pendulum. Damping may also be effected by a permanent magnet device 24 coacting with an electrically conductive cupola 25 on the pendulum. The transparent zone of the analysis surface 6 may have a shape other than the heart shape shown in Fig. 5, i.e. a shape defined by a spiral curve similar to the curves 7 or 8 of Fig. 5 on the one hand and a straight radial line on the other hand. Furthermore, instead of being transparent and opaque the two zones may be reflective and light-absorbent respectively in which case the light source 13 and the photo cell 9 are disposed on the same side of the surface 6, light reflected from the surface being further reflected to the photo-cell by a halfsilvered mirror disposed at 45 degrees to the axis X-X.