Patent GB-806641-A (GB)
Title: Improvements in servo controlled phasemeters
Inventor: CRAZALAS ANDRE
IPC: G01R25/00
Filed: 1955-07-29
Abstract: 806,641. Phase measurement. COMPAGNIE POUR LA FABRICATION DES COMPTEURS ET MATERIEL D'USINES A GAZ. July 29, 1955, No. 21968/55. Class 37. [Also in Group XXXVIII] A servomotor-controlled phasemeter indicating the phase difference between two electrical signals comprises a bridge phase detector with an asymmetrical conducting device and a series non-linear resistance in each arm, to alternate diagonals of which the respective signals are applied to generate an output controlling a servomotor, which adjusts a phase-shifter in series with one signal for zero phase detector output, and drives a mechanical indicator for the phase difference ; one input signal being a reference signal and the other derived from a second phase shifter responsive to a mechanical input to be remotely transmitted. Fig. 1 shows a phase detector 1 comprising a bridge rectifier, network having a non-linear resistance in series with each rectifier receiving an input signal E1 of phase angle #1 on one diagonal, and on the other diagonal the output of an electromechanical phase-shifter 6 (which may be a selsyn unit) energized from an input signal E2 of phase angle #2. The unidirectional output of the phase detector proportional to the cosine of the phase difference between the signals at its diagonals is amplified at 2 and applied to control the rotation of D.C. servomotor 3 driving indicator 4 and proportionally through gearing 5 the movable member of the phase-shifter 6, to zeroize the detector output when its diagonal signals are in quadrature, and deflect the indicator proportionally to the phase difference between the two input signals. A 90 degree phase-shift circuit may be inserted in series with either input to the phase detector so that its output is zero when the respective inputs are in phase, and the detector output may be chopped for A.C. amplification and operation of a twophase A.C. servomotor. Fig. 2 shows a followup system wherein an input magnitude X is converted by device 10 (which may be a selsyn unit excited from a reference alternating voltage) into an alternating signal the phase angle of whose fundamental varies linearly with the input magnitude, which is applied to phase detector 1 for comparison with the output of phase-shifter 6, energized from the reference voltage to produce an output signal which after amplification at 2 controls servomotor 3 to derive an output magnitude Y and to drive proportionally through gearing 5 the movable member of phase-shifter 6, so that the output magnitude Y is proportional to the input magnitude X with the introduction of a constant which is the inverse 1/X of the step-up ratio of gearing 5. The latter is replaceable by mechanism introducing any desired non-linear function whose inverse function is introduced into the relationship between y and x; i.e. the dy introduction of functions x=-, x=y(t)dt for the dt dx relationships y=x(t)dt, y=-. Remote transdt mission may be achieved by modulating the variable and reference phase signals upon carrier signals, transmitted over channel XX, filtering, demodulating and amplifying to energize the phase detector 1 and phase-shifter 6 at a remote station. Specification 784,356, [Group XXXVIII], is referred to.