GB759585A - Improvements in and relating to accelerometers - Google Patents

Abstract

759,585. Electric measuring systems. BRITISH THOMSON-HOUSTON CO., Ltd. March 24, 1953 [March 24, 1952], No. 7519/52. Class 40(1) An accelerometer comprises a movable armature centrally mounted between two pairs of salient poles the axes of which are perpendicular, one pair of poles carrying A.C. energized coils and the other pair of coils in which current is induced when the armature is displaced from a mutual position along the axis of the first pair of poles, means being provided for producing from this current a voltage of such sense and magnitude that when applied to the coils on the first pair of poles creates a force tending to restore the armature, this voltage being used as a measure of acceleration along the axis of the first pair of poles. For measuring acceleration along the direction x-x only, Fig. 1, current from an A.C. source 4 flowing in the motor windings 14 and 15 induces an e.m.f. in opposing position-sensing coils 16 and 17, the resultant phase and magnitude of which correspond to the direction and magnitude of the armature displacement from its zero-central position. This e.m.f. is amplified at 5 and fed through a phase-sensitive detector 6 stabilizer network 7 and amplifier 8 to coils 14 and 15. The interaction of the flux produced by this current and by a fixed D.C., from source 12 in the opposed coils 16 and 17 causes a restoring force on the armature which balances the accelerating force. The output of detector 6, which is thus proportional to the acceleration, is measured at 9, 10. In a modification for measuring mutually perpendicular acceleration components Fig. 2, a further four coils 19, 20, 21 22 having similar functions to those described above are mounted so that the two pairs of motor coils 14, 15 and 20, 22 are on poles at right angles to each other as are the pairs 16, 17 and 19, 21 of position sensing coils. The two pairs of motor coils are supplied from respective sources 4, 4<SP>1</SP>, with currents of different frequency or of the same frequency but in phase quadrature so that the induced currents in the two pairs of position sensing coils, which are amplified together at 5, produce outputs only in appropriate detector 6, 6<SP>1</SP>, and motor coils, these outputs being proportional respectively to the components along the axes of these coils and measured at 9-10, 9<SP>1</SP>-10<SP>1</SP>.