GB1015153A - Rotation measuring device - Google Patents

Abstract

1,015,153. Measuring rotation electrically. STANDARD TELEPHONES & CABLES Ltd. Sept. 21, 1962. [Sept. 26, 1961], No. 36014/62. Heading G1N [Also in Division F4] A rotation sensing device consists an anisotropic paramagnetic element arranged in a magnetic field produced, for example, by means of a circulating lossless current, the field having a fixed orientation in space, and means for sensing changes in the relative angular positions of the element and the field. A crystal 9 of diphenyl picryl hydrazyl is mounted by arm 11 inside a spherical quartz shell 2 having 50 A thick layer 3 of lead on its inner surface. The assembly is cooled sufficiently to make the lead superconductive and a circulating current 10 is induced in it to provide a magnetic field H which acts at right angles to the longitudinal axis of the crystal 9. A coil 12 is wound round the crystal and is energized with radio frequency current at the atomic or nuclear resonant frequency of the crystal at the preset orientation relative to field H. A sensing coil is provided at right angles to field H and to coil 12, and detects the amount of r.f. energy absorbed by the crystal. If the assembly is rotated the magnetic field H remains in its initial direction in space and so acts at a different angle to crystal 9, so changing the resonant frequency. The r.f. frequency is changed to the new resonance frequency which is a function of the angle of rotation. In the preferred arrangement (Fig. 3) the output from a crystal oscillator 46 is frequency modulated at a lower frequency from oscillator 48 and the modulated signal is applied to frequency multiplier 49 whose output is fed to coil 12. The output from the sensing coil is amplified and its phase is compared at 52 with a reference phase from oscillator 48. The low frequency signal detected by the sensing coil will be in phase or out of phase with the oscillator output depending on whether the r.f. signal frequency is above or below the crystal resonance frequency. The output from comparator 52 is applied to a servo control system which controls crystal oscillator 46 until resonance is restored. The frequency of the crystal oscillator is compared at 54 with the frequency of an atomic clock 55. The difference frequency is applied to a frequency counter 56 whose output may control directly the attitude of a vehicle in which the apparatus is mounted, or may be fed to a computer. Additional similar devices may be oriented along different axes to provide additional information. A cryostat for containing the device is described (see Division F4).