| 摘要 |
1,178,572. Measuring velocity. EBAUCHES S.A. 11 April, 1967 [27 April, 1966], No. 16530/67. Heading G4H. [Also in Division G1] Apparatus for measuring the muzzle velocity of a bullet 3, Fig. 1, comprises two coils 1, 2 coaxially arranged round the muzzle of the canon, which are connected in parallel with capacitors 4 in a circuit 5 energized from an H.F. oscillator 6 whose frequency is adjusted to the resonant frequency of the circuit 5 in the absence of a bullet. The output from circuit 5 is fed to a demodulator 8 whose output is direct-current coupled to a trigger circuit 10. The amplitude of the oscillator 6 is adjusted, in the absence of a bullet so that the output signal from the demodulator has an amplitude Vo, Fig. 2. When a bullet .passes through, the circuit 5 is momentarily detuned so that. the demodulator output has the form of pulses of duration equal to the time taken for the bullet to pass through the coils. The trigger circuit 10 is arranged to be released .at a voltage level Vd at the beginning of each pulse and restored at a voltage level Ve at. the end of each pulse, thus producing pulses as shown in Fig. 3. The restoration of the trigger circuit changes the state, Fig. 4, of a flip-flop circuit 11, to which it is connected, which in turn opens and closes a gate 12. While the gate is open, for the period T, an oscillator 13 is connected to a counter 14 which provides a digital indication of the time interval T. The distance travelled by the bullet in the time T is measured accurately using a metal object, Figs. 6, 7 (not shown), similar to a bullet which is moved into each coil until the voltage output from the demodulator has reached the level Vd or Ve respectively and the distance between the two portions is metered. A detailed transistor circuit for the demodulator and an output D.C. amplifier is described with reference to Fig. 5 (not shown). |
