Patent GB-671475-A (GB)
Title: Improvements in or relating to means for measuring the magnitude of a condition
Filed: 1949-04-05
Abstract: 671,475. Electric indicating systems. UEHLING, F. F. April 5, 1949. [April 12, 1948] No. 9239/49. Class 40 (i). Apparatus for measuring the magnitude of a condition comprises a circuit including two sources of rectified voltage, one of which produces halfwaves of one polarity and the other of which produces halfwaves of the opposite polarity, so that the source voltages normally balance out; means controlled by the condition to be measured for changing the relative amplitudes of successions of two halfwaves from one source to unbalance the source voltages ; and independent means controlled by the unbalance voltage to vary the relative amplitudes to rebalance the voltages and indicate the magnitude of the condition. Fig. 1 shows a telemetering system wherein the winding 12 of a transformer 10 energizes a symmetrical loop circuit comprising equal series resistors 15, 16 and similar rectifiers 17, 18 of opposing polarities. A similar loop circuit comprises equal series resistors 21, 22 and opposed rectifiers 23, 24 interconnected by a potentiometer 26, energized by a winding 13 in series with the junction of the resistors 21, 22, the potentiometer slider, and lines 41, 42, which are connected to the slider of a remote transmitter potentiometer 53, operated by a waterlevel float 58, and to the junction of similar opposed rectifiers 51, 52 connected to the ends of the potentiometer. The receiver resistors 15, 16, 21, 22 are connected in series across the input of an amplifier 31 feeding one winding of a two phase motor 32 driving the slider of the potentiometer 26 and the indicator pointer 37, the other motor winding being energized from the A.C. supply through a phase-shift condenser 36. When the transmitter and receiver potentiometer sliders are in mid positions a positive-going fullwave rectified signal in which successive halfwaves are equal appears across 15, 16 and is balanced by a similar signal across 21, 22 so that the amplifier input is zero and the motor remains at rest. The amplitude of the signal across 15, 16 is adjustable by the rheostat 20 and on deflection of the transmitter slider in either direction from its mid position, the signal across 15, 16 remains unaltered, while the respective increase and decrease in the potentiometer legs in series with the rectifiers 51, 52 correspondingly increases and decreases the amplitudes of successive halfwaves of the rectified signal across 21, 22 in accordance with the magnitude and sense of the deflection, so that the resultant signal applied to the amplifier is an alternating voltage whose amplitude and phase are representative of the deflection magnitude and sense. The motor 32 rotates and readjusts the receiver slider until the respective increase and decrease of the potentiometer legs in series with rectifiers 23, 24 is such as to restore the successive halfwaves of the signal across 21, 22 to equality and to reduce the amplifier input signal to zero, so that the motor stops and the indicator 37 is positioned in correspondence with the new liquid level. Similar results are obtainable by comparing a steady half wave rectified voltage with another whose amplitude varies from the balance value in accordance with the magnitude and sense of the deflection to be transmitted. The A.C. energized rectifier pairs may be replaced by two sources of unidirectional pulsating voltage in synchronized opposition (e.g., bipolar generators) in one of which the amplitudes of alternate halfwaves are adjustable in accordance with the sense and amplitude of the deflection to be transmitted. The device is applicable to the transmission of other deflections.