GB782266A - Improvements in and relating to waveform-shaping circuits and to electronic phase-angle measuring apparatus - Google Patents

Abstract

782,266. Measuring phase angle differences. ENGLISH ELECTRIC CO., Ltd. April 1, 1955 [April 2, 1954], No. 9821/54. Class 37. [Also in Group XL (c)] Electrical apparatus for the measurement of the phase displacement between two alternating or pulsating voltages va and vb, Fig. 1, comprises amplifiers 1a, 1b arranged to apply signal voltages of substantially constant amplitude Va, Vb through a feed-back circuit (Fig. 6, not shown), to waveform shaping circuits 2a, 2b (see Group XL (c)), a supply 4 of constant direct current, a moving coil ammeter 5 reading phase angles directly in degrees, and an electronic switch 3 operated on and off by the two resulting output waveforms VA, VB, from the circuits 2a, 2b to pass an average current depending upon the phase angle difference through the meter 5. In operation, the waveforms va, vb, amplified to Va, Vb, Fig. 2, having a phase difference p which it is required to measure are converted by the circuits 2a, 2b into rectangular waves VA, VB, having a mark/space ratio which is variable but should preferably be 1:1. The leading edge of waveform VA operates the switch 3 to make the contact 3b and cause current to flow through the meter 5, whilst the leading edge of VB changes over the switch 3 to make contact 3c and short the meter 5. The resulting current, Fig. 2e, has an average value which is proportional to the phase difference, and this average value is measured by the meter directly in phase angle degrees. If small phase angles are to be measured the voltages VA1, VA2, from the circuit 2a may be given a phase angle difference of 180 degrees, the required signal being selected by a range switch 7.