Patent GB-743675-A (GB)
Title: Improvements in phase meters applicable to torque measurement
IPC: G01R25/00
Filed: 1953-04-13
Abstract: 743,675. Electric indicating systems. SAUNDERS-ROE Ltd., DAVIES, G. N.. and MOSS F. P. Dec. 24, 1953 [April 13, 1953], No. 10009/53. Class 40(1) [Also in Group In a phasemeter responsive to the phase angle between two sinusoidal waveforms of the same frequency wherein the latter are converted into square 'wave trains having a similar phase relationship which are mixed to derive a unidirectional current representing in magnitude the phase angle between the sinusoidal waveforms, the mixer is a pentode having: one square wave train applied to its control grid and the other square wave train applied to its suppressor grid. with an integrating moving, coil indicator connected in its anode circuit, For determining torque as a function of angular twist of a shaft using such a phase indica- 57 tor, the output of a phonic wheel generator driven from a point of the shaft is received by an AVC controlled amplifier A wherein a variable gain pentode V1 is resistance coupled to a fixed gain pentode V3 whose output is rectified by a diode V5, against a variable cathode delay bias derived from the slider of potent'ometer R19 energized from the junction of gas filled Stabilizing tubes V9, V10 across a high tension supply. to develop a gain controlling negative bias voltage applied to the grid of V1. The amplified output of V3 is coupled by capacitor C13 to the interconnected cathode and anode of a pair of reversed limiting diodes V6 together with a positive bias from the slider of potentiometer R27 across a high tension supply. the remaining cathode and anode being returned to the positive line to the junction of V9 and V10. The point X of the anode of the second diode of V6 in amplifier A is connected over series resistances to the suppressor grid of pentode V8 whose cathode is returned to the positive junction of V9. V10 while the anode is connected to the H.T. supply over variable resistance R40, in series with fixed resistor R39..in parallel with an integrating indicator M (a milliammeter), in series with a fixed resistance R38. The output of a second phonic wheel generator driven from a separate point of the shaft is received by a similar AVC controlled amplifier 3 comprising a double diode limiter V7 the anode of whose second diode is connected to the control grid of pentode V8 over series resistances so that the control and suppressor grids receive trains of positive going square waves synchronous with the phonic wheel generator outputs, and of amplitudes set by R27 such that the pentode grids are never driven positive .with respect to the cathode, and the valve passes current pulses only during the periods during which both grids receive a positive going pulse, the width of the anode current nulses being dependent on the phase difference. It is shown that the mean anode current is also dependent on. the phase difference between the pulses, being a maximum for phase coincidence, and the indicator M is calibrated to indicate the phase difference directly. from which the shaft torque may be determined. The H.T. supply is derived from a fullwave stabilizing rectifier valve V11 ener- ,gized by a constant voltage stabilizing transformer Tl also supplying the heaters of valves V6. V7, V8 of the apparatus; the remaining valve heaters being supplied from transformer T2. In setting up for operation in the absence of input signals the 4 position 3 gang switch SW1 is placed in position Z to connect the control grid, suppressor grid and cathode of valve V8 and shunt the indicator M to half sensitivity by resistance R37. Resistance R40 is varied until the meter reads zero at full scale deflection and the switch is set to position B at which the meter shunt R37 is removed and the suppressor grid only is connected to the cathode. Resistance R27 in amplifier B is adjusted until the indicator reads zero, and the switch is set to position A at which the control grid only is connected to the cathode, and resistance R27 of amplifier A is adjusted for zero indication. The switch is then set to position U at which both control and suppressor grids are disconnected from cathode and the anode current of V8 deflects the indicator to show the phase angle between the input signals.