discussed in the sublparagraphs below. Recording Oscillographs Consolidated Engineering Corporation, Type 3~114-P-3, 18-chan- nel recording oscillographs were used to record all response measurements. Selection was based upon previous experience which indicated this equipment, if properly installed, would adequately record the desired data under the anticipated test conditions. Further, the equipment was immeciiately available. The oscillograph was made insensitive to aircraft vibrations and blast-induced shock accelerations by simple shock mounting. No special modifications, other than provisions for increasing papespeed by overriding the governor, were deemed necessary, Pertinent information relative to the oscillograph and operation thereof is summarized below: a. b. Active data channels Power . . . . Ce Paper width d. e. f. PRC Scpe Tengen or ye 4 pad Wee eakdebe ase) Sa ‘sheng siabtery3 eee, : ae ey fos au . . . ° Record speed used . . . 6 in./sec recording time Timing marks . . . . . Paper length. . Approximate maximum . . . . 7 in. . 125 ft . 250 sec «. 0.01 sec intervals ' Outputs from the sensing elements are in the form of fluctuating DC voltages. Operation of the oscillograph depends upon converting the electrical output of the various gases into a proportional galvanometer deflection that can de recorded as a function of time. To accomplish this, oscillographs are equipped with galvanometers of the D'Arsonval type having a mirror attached to the upper tension support. Thus mounted, the mirror follows the movement of the galvanometer coil, To record the galvanometer movements, a beam of light is reflected by the mirror onto a moving sheet of photosensitive paper. The resulting trace on the photozraphic paper is a permanent, time-history record of the variation of the response function being measured, Galvanometers are chosen on the bases of sensitivity and frequency response required for the type of measurement teing made, A separate galvanometer is used for each channel, A Consolidated Engineering Corporation Type 8-104A Bridge Balancing Unit was used to couple the sensing devices to the oscillo- graph and provide the proper bridge voltage and bridge balancing resistance. In addition to the above functions, the bridge unit also provides a known bridge unbalance for calibration purposes, adjusts the input circuit resistance so that the galvanometer is properly damped, and provides for signal attenuation. A schematic of a typical four-active-arm bridge including the bridge balancing unit and oscillograph is shown in Fig. 2.4. Bridge voltage, supplied from a 24 volt aircraft vatter), is adjusted by means of the rheostat shown. The bridge is then taianced by means of the bridge balance potentiometer so that there is no deflection of the galvanometer. If the sensing eiement were now subjected to a measurable input, the «heatstone bridge would tecome unbalanced producing 27 - i" ip a eee ‘ vote A OOD Seg ad RP . ats aes poate g. . . 18, plus one dynamic reference 24-28 volts DC roo 2.3.4.1 rae ena, 8, RO Doren ad re PE | Birte ee = es. bee