603 
33 
Sweep 
Trigger Wire Generator 
Deflection Deflection 
Proportional to Proportional to 
Pressure Time 
ay F 
Condenser 
For Calibration 
Figure 20 - Schematic Diagram of Channel used in Underwater Explosion Tests 
at the Taylor Model Basin 
kilocycles. Its output goes directly to the vertical deflecting plates of a 
Du Mont Type 208 cathode-ray oscillograph. A high-vacuum type of sweep gen- 
erator is used, which produces either single or continuous sweeps. A Hewlett- 
Packard oscillator and General Radio Microvolter are employed for time and 
voltage calibrations. A 35-mm Eastman Ektra camera using an f 1.9 lens re- 
cords calibrations and explosion pressures. The sweep is initiated when a 
fine wire wrapped around the charge is broken by the explosion. 
PART 4, CALIBRATION OF THE PRESSURE GAGES 
The usefulness of a pressure gage for underwater explosions is man- 
ifestly limited by the accuracy and reliability of its calibration. This in- 
volves a precise determination of the electrical output of the gage when it 
is subjected to a known change in pressure. In this section the apparatus 
employed in applying a pressure change to the gage will be described fansite 
then the circuit used in measuring its output by each of several different 
methods. Finally, the results obtained from the various calibrations will 
be compared with one another, with values of piezoelectric constants found 
in the literature, and with values obtained for the same crystals by two 
other laboratories. * 
y The Underwater Explosives Research Laboratory at the Oceanographic Institution, Woods Hole, 
Massachusetts, and the Exploration Laboratory of the Stanolind Oil and Gas Company, Tulsa, Oklahoma. 
