Patent GB-692615-A (GB)
Title: Improvements relating to devices for examining waveforms
Inventor: MCQUEEN JACK GORDON
IPC: G01R13/34
Filed: 1949-10-21
Abstract: 692,615. Cathode-ray oscillographs. METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Oct. 12, 1950 [Oct. 21, 1949], No. 27132/49. Class 37. In a system for converting a recurrent electrical waveform having a high recurrence frequency into a corresponding waveform having a lower recurrence frequency, the input waveform is gated by high recurrence-frequency gating pulses whose timing is progressively varied at the lower recurrence frequency and the output from the gating circuit is integrated to give the required waveform, which may be displayed or recorded by a cathode-ray or electromechanical oscillograph or recorder. As shown in Fig. 2, the waveform to be converted is triggered by a " master pulse " applied through a " fixed delay 1 " and the gating pulses are generated by applying the master pulses through a " variable delay 1 " to trigger a flip-flop V2, V3, Fig. 3, whose positive pulse output is applied through diode clamps D1, D2 and valve V4 to discharge capacitor C5 in the " fast sweep " circuit thereby producing a steep negative saw-tooth voltage which is applied to the grid of V5. The cathode-coupled valves V5, V6 comprise the " trigger " circuit and a negative saw-tooth output from the Millertransitron " slow sweep " oscillator V1 is applied to the grid of the normally cut-off valve V6 so that it becomes conductive when the grid potential of V5 falls below that of V6, thereby producing a negative pulse at the anode of V6 whose timing is progressively delayed and which trigger a " pulse generator " producing a short negative gating pulse which is fed to the cathode of a pentode " gate " V14, Fig. 5 (not shown). The positive high-recurrence frequency waveform is applied to the signal grid of the gate and the amplified gated output is fed to an integrating cathode follower V18, Fig. 5 (not shown), whose cathode load comprises a capacitor (C22) shunted by a triode (V19) to which positive gating pulses are applied so that the capacitor is changed to a voltage proportional to the amplitude of the waveform at the gating instant, the change being maintained until the next gating period. The resultant slow sweep waveform may be applied to the Y-plates of a cathode-ray tube having the slow-sweep saw-tooth from V1 as time base, Fig. 1 (not shown), but when the high-speed waveform is likely to jitter with respect to the master pulse the time-base sweep voltage is synchronized by the waveform as shown in Fig. 2 by triggering a " time base," V10, C12, Fig. 4 (not shown), from the waveform generator through a " variable delay circuit 2 " (V7-V9) to generate a positive sawtooth which is terminated by a timing circuit (V11) receiving a positive pulse from the " pulse generator " through " fixed delay 2," the sawtooth output being integrated in a smoothing circuit (V12, V13) similar to V18, V19, Fig. 5 (not shown), to give a steadily increasing voltage which is applied to the X- plates. Instead of displaying the resultant waveform on the screen of a cathode-ray tube it may be recorded by deflecting a light spot across a photo-sensitive paper moving synchronously with the slow sweep or by a pen and recording chart. If it is desired to examine a portion of the waveform additional means may be provided for adjusting the position of the gating pulse manually.