641 
ELECTRICAL INSTRUMENTS FOR STUDY OF UNDERWATER EXPLOSIONS 
AND OTHER TRANSIENT PHENOMENA 
Abstrast 
This report contains diagrams and brief descriptions of 
electronic circuits used at the Underwater Explosives Research 
Laboratory for recording transients: amplifiers for cathode- 
ray tubes, time bases, time delays, and calibration equipment. 
Most of these circuits are intended primarily for use with 
piezoelectric pressure gauges but are readily adaptable to 
other types of gauge or pickup. Related pieces of apparatus, 
such as master control units, cameras, and special firing cir- 
cuits, are also described, The requirements to be met by 
equipment used in recording transients are discussed at some 
lengthe 
I, INTRODUCTION 
In order to examine the properties of underwater explosions and their 
effects it is very desirable to be able to obtain a continuous record in 
time of such quantities as pressure, acceleration, and deformatione The 
most powerful class of tool for doing this is an appropriate eleetrical 
"transducer" for developing electrical signals proportional to the mechani- 
cal quantity. This is followed by a recording cathode-ray oscillograph to- 
gether with appropriate auxiliary equipment for its operationg The purpose 
of this report is to make available details of circuits which have been 
successfully used at the Underwater Explosives Research Laboratory (UERL), 
together with some discussion of the requirements for such circuits and 
their operation. Very little of the equipment described is wholly original -- 
some of it having been adapted from commercially available instruments — and 
much of it has room for improvement. It has, however, been developed suffi- 
ciently to obtain useful results in field work with reasonable precision. 
This report is written in the hope that information about such equipment will 
be of use to others. 
The bloek diagram (Fig. 1) represents the, various elements involved in 
recording transients by a cathode=ray tube. The signal from the gauge or 
pickup is ordinarily too small to be applied directly to the cathode=ray 
tube without an intermediate amplifier, and a voltage calibration of the 
amplifier and tube is necessary. For a permanent record of deflection 
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