Patent GB-815481-A (GB)
Title: Improvements in or relating to electronic apparatus for timing events
Inventor: NUTTALL THOMAS CAYTON
IPC: G04F10/06
Filed: 1955-10-19
Abstract: 815,481. Electric time interval measurement. RANK CINTEL Ltd. Oct. 19, 1956 [Oct. 19, 1955], No. 29839/55. Class 37. Apparatus determining the instant of occurrence of an event in relation to a timing oscillation of known frequency utilizes the event to generate an electric step signal corresponding in timing thereto, which is applied to a selective circuit to develop therein a ringing signal at a frequency equal to an integral submultiple of the timing oscillation; from which ringing signal and timing oscillation signals of like frequency are derived and are applied to a display device wherein their phases are compared to produce a visual indication of the timing of the occurrence. In Fig. 1 the occurrence of an event to be timed triggers generator 2 of a step function voltage (Fig. 2) having a short rise time and predeterminedly timed with respect to the instant of the event (which may e.g. be the passage of an object past a fixed point or a photo-electric cell). The signal is applied to a selective amplifier containing at least one low decrement oscillatory circuit tuned to e.g. 10 Mc/s., which is driven to ring by the transient at this frequency (Fig. 3) and the resultant signal is applied to balanced demodulator detectors 5, 6, also supplied with a pair of quadrature signals from phase changer 7 driven by master oscillator 8 generating a frequency identical with that of the selective amplifier (50 Mc/s.). The resultant output pulses (Fig. 4) have profiles similar to those of the corresponding envelopes of the ringing signal and are applied through matched linear phase-splitting amplifiers 9, 10 to the X and Y deflection plates of long persistence cathode-ray oscillograph 13, whose trace is brightened for display by electrode 16 over a time set by resistance-capacitance circuit 20, 22 pulsed by multivibrator 4 triggered by the occurrence of the initiating event. Since the amplitudes of the deflection Y signals are such that - = the tangent of the X phase angle between the ringing voltage and the standard oscillation, the oscillograph displays a bright radial trace indicating by its orientation the timing of each event generating a step function with respect to successive cycles of the standard oscillation, enabling the screen to be calibrated radially in values of 1 to 9 hundredths of microseconds for a 10 Mc/s. standard oscillation. In a modification (Fig. 5, not shown) there are provided three separate timing devices as above, energized from a common step generator and having a common brightening pulse generator for their respective oscillographs, but having selective amplifiers tuned respectively to 10 Mc/s., 1 Mc/s., 100 Kc/s. and supplied with pairs of quadrature signals at 10 Mc/s., 1 Mc/s. and 100 Kc/s. derived from a master oscillator and two successive decade frequency dividers, wherein the three oscillograph tubes are adjacently mounted in a decimally calibrated panel (Fig. 6, not shown) and respectively read microseconds, 0.1 microseconds, and 0.01 microseconds to time the initiating even to 9.99 microseconds with 0.01 microsecond accuracy. In a further modification (Fig. 7, not shown) the selective amplifier oscillatory circuit is tuned to resonate at 5 Mc/s. and its ringing signal is applied to the balanced demodulator detectors through a frequency doubler circuit. The master oscillation and the ringing signal may be applied to deflect the oscillograph in respective co-ordinate directions giving an ellipsiform spiral display whose major axial inclination represents the phase difference. Plural (e.g. 5) phase-sensitive detectors may receive the ringing signal together with a respective one of a series of master oscillations each shifted in phase by 72 degrees with regard to its predecessor, and the detector outputs may be applied through oppositely poled rectifiers to a pair of trigger circuits, each of which changes over from one stable condition to another when the applied signal is within a small range of its possible maximum and the ringing signal is approximately in phase (or antiphase) with the master oscillation, so that the trigger circuits may each operate one of a decade display of indicator lamps showing the timing of the input event, or may directly feed such information to a computer in decade notation.