GB772833A - Improvements in or relating to indicating systems - Google Patents

Abstract

772,833. Measuring velocity of shock waves. TITTERTON, E. W. Sept. 20, 1948 [Sept. 30, 1947], No. 24637/48. Class 118 (2). [Also in Group XXXVI] A system for measuring the velocity of shockwaves, such as detonation waves in explosives, comprises a plurality of circuit-closing devices 20, 21 . . . 22 operated by the passage of the shock-wave (see Group XXXVI), and each arranged to discharge an associated charged condenser 13, 14 . . . 15 into a common conductor connected to a cathode-ray oscilloscope 26, via a damping resistor 23 and co-axial cable 25. The composite pulse displayed enables the speed of the shock wave to be determined. The individual rapid discharges build up a charge on condenser 12 to produce a pulse as shown in Fig. 4. Ideally, six devices 20, 21 . . . would give a trace as at 50, or, if closed simultaneously, as at 51. In practice, however, each discharge has a shape as at 52 and simultaneous closure of the devices produces a trace as at 53. The occurrence of successive closing gives a trace as at 54, the height of which can be observed or recorded photographically. The charging resistors 17, 18 . . . 19 are large enough to provide a long time constant with their associated condensers 13, 14 . . . 15, whereby multiple switch closings, or shorting of leads, produces little or no effect in the trace. The cathode-ray oscilloscope may show fiducial timing pulses as indicated in Fig. 1 from a suitable pulse generator (not shown). The height of the output trace is a somewhat non-linear function of the number of switches closed within the time constant of condenser 12 and resistor 24. A modification (Fig. 3, not shown) to avoid this non-linearity comprises alternate positive and negative potentials on the condensers such that instead of a cumulative pulse a series of small pulses alternately up and down, as at 55 in Fig. 4, are produced.