710 
aM 
and may foul the rig and even bring the vessel into scrious trouble. There 
is always some bow in the side spaccr cables due to the drag of the water, 
which causes an uncertainty with respect to the angle between the gauges 
and the charge and the gauge=to-charge distances, However, this uncertainty 
in gauge-to-charge distance may be overcome by comparing the results for.an 
asymmetrical charge to results for a symmetrical charge fired under identical 
conditions. For the piczoclectric gauges used off the sides of the charge 
there must be a separate rcturn line along the surface to carry the gauge 
cablese 
The difficulties encountered witn the paravane rig probably outweigh 
the advantage in obtaining values regarding the pressure field in two dimen- 
sions. The same results could be obtained more rapidly and with less 
trouble by using the one~dimensional rig and firing twice as many charges. 
he Instrumentation 
The instrumentation may be generally divided into two types -—- piczo= 
electric and mechanical. The piezoelectric instrumentation gives rather 
complete fundamental information about the explosive shock wave in the water 
but is difficult to maintain and operatce On the other hand the mechanical- 
gauge instrumentation is casy to maintain and operate and is very reliable, 
but the results are muah harder to interpret in terms of the shock-wave 
parameters. 
(a) Piezoelectric-gauge instrumentation. —- The instrumentation with 
piezoelectric gauges consisted of the following groups: gauges, transmission 
lines with their compensating networks, amplifying and recording aquipment, 
time- and voltage-calibrating equipment, 
(i) Gauges. The piezoclectric gauges used in this work were composed 
of 1, 2, or 4 tourmaline eloments [2,3]. The ones usually employed were of 
the doublet type with a gauge constant of roughly ) «pscoulomb/(1b/ing). 
(ii) Transmission of gauge signals. The transmission system for bring- 
ing gauge signals to the RELIANCE consisted of the following elements: a 
copper tube with central conductor attached to the gauge and running directly 
back in the opposite direction from the charge for a distance of 20 ft where 
it was spliced to a Miller plug. From the other side of the Miller plug 
Army-Navy Type RG-l1/U concentric cable ran up to a surface buoy. The 
length of this section of the cable varied from 0 to 80 ft depending upon 
the particular location of the gauge. This cable terminated in a second 
Miller connector at the surface buoy, where there was inserted a compensate 
ing patch cord containing a resistance-capacitance network which was a part 
of the double-ended cable compensation uscd with the RELIANCE—type gear. 
(Such compensation is necessary to correct for frequency response and di- 
electric absorption on long cables [u].) This patch cord was connected in 
turn to a 600-ft length of RG+l1/U cable which ran back along the surface 
to the recording vessel, terminating at the large cable-reel on the deck. 
A 20-ft section of the same cable carried the signal from the reel down to 
the input of the compensating network in the master control panel. 
