Patent GB-606269-A (GB)
Title: Improvements in electrical counting and time measuring arrangements
IPC: H03K25/00
Filed: 1945-06-30
Abstract: 606,269. Measurement of short-time intervals; phase and frequency measurement. SPERRY GYROSCOPE CO., Inc. June 30, 1945, No. 16662. Convention date, June 30, 1944. [Class 37] [Also in Groups XIX and XL (c)] Relates to a system for measuring a time interval by counting the number of cycles of a known frequency occurring in the interval and consists in connecting a condenser to be charged to a value corresponding to the number of cycles at the beginning of the interval, and at the end of the interval connecting the condenser to an indicator. The system may be used for phase measurement, when the interval is that between corresponding points' of two periodic waves; or it may be used for frequency measurement, when the interval is that between corresponding points of successive waves. Measurement of phase difference.-Two waves from sources 11, 12, Fig. 1, whose phase difference is to be determined are applied to an interval wave generator 16 to produce a rectangular pulse commencing at one point of one wave and ceasing at the corresponding point of the other wave, so that the pulse duration is related to the phase difference. This rectangular pulse is applied to an electronic switch 18 to allow a train of waves of known frequency to pass from generator 17 to a blocking oscillator 19 during the duration of the rectangular pulse. The blocking oscillator 19 is adapted to produce one pulse for every alternate wave in the received train. This train is applied to a series of counters 21 ... 25, each of which is adapted to store pulses, e.g. up to five, on a condenser, which discharges at e.g. every fifth pulse to produce a pulse to be applied to the next counter. Thus, after the cessation of the train, each element of charge on the condenser of counter 25 represents 1000 cycles, each element of charge on the condenser of counter 24 represents 200 cycles &c. The rectangular pulse from 16 is also applied over a delay device to a generator 29 to produce a pulse at the end of the rectangular pulse, which unblocks electronic switches 28, 33, thus allowing the charges on the condensers of the counter to be applied to amplifier 32, 36, to actuate indicators 13, 14. The indicator 13 registers thousands of cycles by a suitable mixture of charges from counters 24, 25; similarly indicator 14 registers hundreds of cycles. Indicator 15, however, registers tens and fractions of a cycle, since it is fed through an amplifier 41 and an electronic switch 39 from a saw-tooth oscillator 37 consisting of a condenser charged by the rectangular pulse from generator 16 and discharged every ten cycles by the pulse from counter 21 over lead 50. The amplifier 32, 36; 41 have long time constants so that the readings are maintained from train to train. The condensers of the counters are all discharged at the end of the rectangular pulse by a pulse from a generator 42. Counter device.-A counter, Fig. 3, has pulses 81, Fig. 4B, applied at 51 to a cathode 53 and anode 54 of a double diode; the negative portions pass over anode 63 to the cathode load 66 of a cathode follower 65 to earth; the positive portions pass from anode 54 to cathode 56 to charge condenser 57, whose charge increases in steps 83, Fig. 4E, until at every fifth pulse it reaches a potential sufficient to actuate the blocking oscillator 59, 58, 61 to discharge condenser 57 and produce a pulse 85, Fig. 4D in the transformer 62 which passes to the next counter over lead 77. A cathode follower 72 supplies the voltage on condenser 57 to the indicator over lead 35. Electronic switch and amplifier.-A preferred electronic switch and amplifier, Fig. 5, has the unblocking pulse applied at 30 to cut-off current flow through resistance 109 and render the diode 105, 105 non-conducting. Valve portion 94 then responds to the voltages applied over leads 34, 35 from the counter to charge condenser 96 to a corresponding potential; this potential is applied to valve portion 98 which acts as a cathode follower to supply the indicator 14, whose zero setting may be adjusted by potentiometer 103 and whose calibration may be adjusted by potentiometer 101. Saw-tooth generator.-The saw-tooth generator 37, Fig. 1, has the rectangular pulse from generator 16 applied at 40, Fig. 7, to render diode 123 conducting to charge condenser 121; pulses from the counter 21 are applied at 50 to render pentode 129 conducting to discharge the condenser every tenth cycle. The charge on the condenser 121 at the end of the train is applied over cathode follower valve 134 to the electronic switch 39, Fig. 1, amplifier 41 and indicator 15. Frequency measurement.-In a modification adapted for measurement of audio frequencies, the audio frequency is charged into pulses of length corresponding to'half the period of the audio frequency and these pulses are applied to shock excite a stable oscillator, Fig. 2, (not shown), to provide the interrupted train to be applied to counters 19 ... 25 of Fig. 1.