GB1310302A - Apparatus for generating a signal representative of the heading angle of a body - Google Patents

Abstract

1310302 Measuring magnetic heading electrically SPACE AGE ELECTRONICS Ltd 17 May 1971 [26 May 1970] 25337/70 Heading G1N Apparatus for measuring the heading of a craft with respect to the Earth's magnetic field comprises two pendulously mounted magnetic-field-responsive current conducting devices arranged so that deviation of the craft from a datum heading causes the Earth's magnetic field to increase the impedance of one device and decrease that of the other device, and means to detect the difference between the currents flowing through the two devices. As shown, a ring 1 of highly permeable magnetic material is pendulously supported in a frame 28 by bearings 27. The ring 1 carries two symmetrically disposed coils 2, 3 positioned, by rotation of knob 33 about pivot 29, so that when the craft is on course, the Earth's field affects both equally. The coils are energized with pulses of current, derived by half-wave rectification of the output of oscillator 5, of amplitude to not quite saturate the ring 1. Deviation from the set heading unbalances the currents in the windings 2, 3 which unbalance is fed, via transformer 9, phase sensitive detector 14, and amplifiers 17, 18 to an indicator 21 or to a course-correcting control, e.g. ships rudder control (not shown). Coils 2, 3 may be uniformly wound in which case the output is approximately proportional to the sine of the angle of deviation, or the coils may be bunched in their middles to give a linear output. Printed circuit boards 35 each carry two circular conductive tracks to which the coils 2, 3 are connected and via brushes (37) to the transformer 9. The common connection to diode 8 is made via the pivot 29 and brush 38. Two boards 35 are provided to enable the apparatus to be used either way up.