807 
~Qe- 
(ii) Result with single-ply 3" x 1/16" gauge for a spherical 
charge. 
On Plate 9, Record 6 is a typical signature obtained from a 14 oz. 
P.E. spherical bare charge. The extremely sharp rise, overshoot and fairly 
smooth decay is to be noted when the gauge is direoted face-on to the 
pressure Wave, 
Although it now appeared that the most practical type, of miniature 
gauge for general purposes was probably to be of dimensions 5" in diameter 
and 1/16" in thickness, and that the construction would be similar to that 
given in Appendix 2, it was felt that in order not to lose sensitivity, 2 
two-ply gauge would be neocssary. A two-ply gauge had not yet been 
constructed with very thin silver electrodes sintered onto the crystal 
faces, and moreover the single=-ply had not been really tested edge-on with 
the orystal faces perpendioular to the water surface and the cable leading 
away from and perpendioular to the pressure front. It was also felt that 
it would be worth exploring a gauge only 1/32" thick as well as a gauge 1" 
in diameter and $" thick. Circumstances might arise where this latter- 
sized gauge with double the thickness might be used. For example an 
approximate thooretical calculation revealed that whereas a 14 1b. charge 
fired at a 3" gauge edge-on caused a peak pressure to be recorded 3% less 
in value than the true peak pressure, the error would not be greater than 
about 1% for a 300 lb. charge fired at a 1" gauge edge-on. The tourmaline 
position being slightly precarious, it was thought worth while testing 
gauges 4" in diameter. 
(a) The 4" diameter single crystal gouge. 
. . Three such single-ply gauges were constructed, according to the 
desoription given in Appendix 2. 
Tho gaugswere of thicknesses $", 1/16" and 1/32", 
(b) Results with the 1" single-ply gauges. 
There are no special features to emphasise for the normal face-on 
and edge-on records except that in the former case the time of rise is 
certainly not greater than 1 microsecond but with a definite tendency to 
overshoot at the peak, and the time of rise of the pressure pulse in the 
lattor case is reduced to about 4 microseconds. 
Plate 10, Records 1 to 6 illustrates the pressure pulses recorded 
with the gauges haying their faces perpendioular to the water surface and 
the cable lcading away from the pressure front. Record 1 was obtained 
with the g" thick gauge, the cxplosive being the standard 14" lb. T.N.T. 
charge in its case. Records 2 and 3 were obtained with the 4/16" thick 
gauge, Record 3 being obtained frem a spherical 14 oz. Pez. bare charge 
Without a primer. Reoords 4, 5 and 6 were obtained with the 1/32" thick 
gauge, Record 6 from a spherical 14. oz. P.E. bare charge, and Record 5 
from a bare 14 1b. T.N.T. charge. ‘The spherical charge gave a smoother 
tail to its pressure-time signature than either the oylindrical bare T.N.T. 
oharge or the charge in its standard canister. The pressure pulse 
obtained from the standard charge in its caso is also a little more 
disturbed in its contour than the pulse obtained from the bare charge. 
(0) Tho 4" diamoter single orystal gauge. 
Tho construotion of this gauge is similar to that given in Appendix 2, 
tho thickness of the gauge being $". i oe 
- (a) Results with the 1" diameter single orystal gauge. 
The records obtained from a 4 lb. standard T.N.T. charge, with the 
geuge faco-on and edgo-on are showm on Plato 11, Records 1 and 2 respectively. 
The eevee 
