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INSTRUMENTATION FOR THE MEASUREMENT OF 
UNDERWATER EXPLOSION PRESSURES 
ABSTRACT 
The David Taylor Model Basin, in its efforts to provide instruments 
for the measurement of underwater explosion pressures, has developed three 
pressure gages, two of the piezoelectric and one of the resistance type. The 
construction and operation of the gages are described in detail. 
The most important causes of distortion of a gage signal are ana- 
lyzed, and the measures taken to overcome them are described. In particular 
the mechanical disturbance of a gage cable by an underwater explosion gives 
rise to a spurious signal which is large when ordinary coaxial cables are 
used. An investigation of this effect has resulted in the development of a 
coaxial cable which has many advantages over any other type that was investi- 
gated, and which permits accurate measurements of momentum. 
Several techniques for calibrating the various gages are discussed. 
The best of these methods gives results which agree closely with those ob- 
tained by workers in other laboratories. 
The gages were subjected to explosion tests with charges of about 
one ounce of tetryl, in which pressure-time records were obtained. Only the 
tourmaline gage has been tested with larger charges, of 100 grams or more. 
These tests yield records which exhibit a high degree of reproducibility. 
INTRODUCTION 
When intensive research into the fundamentals of underwater explo- 
sion phenomena was started in the United States less than four years ago, one 
of the first problems encountered was to find a satisfactory gage for measur- 
ing the high-intensity short-duration pressures in the water. 
A number of gages had been developed by previous experimenters in 
this field, some of them mechanical and some electrical, but none of them 
were satisfactory for the new work being undertaken. Mechanical gages such 
as the Hilliar gage (1) (2)* were not fast enough to indicate the rate of 
rise and the peak pressures accurately, and the piezoelectric tourmaline 
crystal gage suggested by Sir J.J. Thomson (3) and used by Keys (4) was, like 
the Hilliar gage, so large that it was suitable only for work with large or 
service charges. 
The rapid progress which had been made in the development of elec- 
tronic instruments in the decade preceding 1940 suggested the use of some 
i Numbers in parentheses indicate references on page 47 of this report. 
