Procédé et dispositifs manométriques applicables notamment à l'étude des phénomènes d'explosion

968, 532. Electric selective signalling. COMMISSARIAT A L'ENERGIE ATOMIQUE. Nov. 26, 1962 [Dec. 6, 1961], No. 44669/62. Heading G4H. In a pressure-measuring device, the pressure to be measured is transformed into a plurality of different pressures in known ratios to it, each acting on a measuring sample mode of a material having a discontinuity in conductivity at a pre-determined threshold value of pressure. Fig. 4 shows one of a plurality of detector units which are mounted on one or more reference plates 16 (all of the same material), the pressure being applied from below in Fig. 4. The pressure may be that of a shock wave from an explosion. In each detector unit, the pressure is changed in a given ratio by a pastille 15 (of a different material in each detector unit) and acts on the measuring sample 14 (of the same material, e.g. sulphur or paraffin, in each unit). If the threshold is exceeded, the change in conductivity is detected by electrodes 19, 20 and signalled to an oscillograph. Since the shock wave may displace the pastille 15 relative to sample 14 so that it short-circuits electrodes 19, 20, a contact probe is placed between pastile 15 and sample 14 (via channel 21) and detects (and displays on the oscillograph) the arrival of the shock wave. Thus this short-circuiting cannot be mistaken for exceeding the threshold, there being two signals spaced apart on the oscillograph when the threshold is exceeded and one otherwise. The oscillograph is triggered by a contact probe 22 actuated by movement of plate 16.