GB1347657A - Magnetic compasses and similar arrangements - Google Patents

Abstract

1347657 Measuring angles FRANCE ARMED FORCES MINISTER OF 19 July 1972 [19 July 1971] 33852/72 Heading G4H Apparatus for measuring the angle between a particular direction and a magnetic field F, e.g. the horizontal component of the earth's field, comprises a motor 1 coupled to rotate a disc 2 and a coil B about an axis x-x<SP>1</SP>, the disc having a single aperture M therein arranged to cooperate with a photo-electric sensing device 4, 5 at a position M 0 , the line joining the axis of rotation to the point M 0 defining the particular direction, the coil having its axis arranged horizontally as shown and equipped with brushes 6 whereby a varying electrical signal may be derived having zero values when the axis of the coil is parallel and anti-parallel with the field, timing means being provided to time the interval between the instant the photo-cell is activated, i.e. the coil is aligned with the particular direction, and the instant of zero value, negative derivative signal from the coil, i.e. the axis of the coil is parallel with the field. The timing means comprises a clock source and a binary counter and binary-digital converter whereby the first instant enables the counter and the second instant stops the counter. For controlling purposes, the counter output may be compared with a desired value to provide a control signal. This process may take place via a radio receiver-transmitter link.