THE REVIEW OF SCIENTIFIC INSTRUMENTS 
831 
VOLUME 21, NUMBER 1 JANUARY, 1950 
Design and Use of Piezoelectric Gauges for Measurement of Large Transient Pressures* 
A. B. Aronst anp R. H. Coret 
Underwater Explosives Research Laboratory, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 
(Received June 22, 1948) 
This report discusses the design and use of piezoelectric gauges for the measurement of rapidly varying 
hydrostatic pressures of large amplitude in gaseous and liquid media. Reasons are given for the selection of 
tourmaline in preference to other types of crystal. Fundamental principles of design are stated, and gauge 
construction is described in the light of these principles. A simplified theoretical analysis of transient response 
characteristics is presented. 
I. INTRODUCTION 
HE original suggestion that transient pressure 
waves could be recorded as functions of time by 
observing the trace of a cathode-ray oscilloscope as it 
was deflected by the signal from a piezoelectric crystal 
has been credited to J. J. Thomson. Early experiments 
using such apparatus to record shock waves from under 
water explosions of TNT were described by Keys in 
1921.1 Since that time, the technique has been applied 
to several types of large amplitude pressure measure- 
ment, the most common being pressure-time phenomena 
in internal combustion engines and in shock waves due 
to explosions in air and water. 
During World War II, a group at the Underwater 
Explosives Research Laboratory of the Woods Hole 
Oceanographic Institution made a number of contribu- 
tions to the technique of shock wave measurement, 
utilizing tourmaline crystal gauges. A discussion of the 
present status of this technique will be given in this 
report. The type of gauge developed at the Underwater 
Explosives Research Laboratory will be referred to in 
the following as the UERL gauge.] 
II. BASIC REQUIREMENTS FOR A PRESSURE- 
SENSITIVE DEVICE 
It is illuminating to- outline first the criteria which 
an ideal electromechanical pressure-measuring device 
should satisfy. Although in principle these criteria 
should apply to any magnitude or duration of applied 
pressure, in practice their relative importance depends 
on both characteristics. In this paper, we consider pri- 
marily the measurement of transient pressures lasting a 
fraction of a second at most and with amplitudes from 
one to hundreds of atmospheres, as opposed to static 
pressures or acoustic waves. The requirements for such 
purposes can be summarized as follows: linearity, 
freedom from hysteresis, thermal stability, freedom from 
* The work described in this report was initiated under contract 
with the OSRD in 1941 and after 1945 was continued under con- 
tract with the Navy Department, Bureau of Ordnance. Contri- 
bution from the Woods Hole Oceanographic Institution, No. 437. 
{ Present address: Department of Physics, Stevens Institute 
of Technology, Hoboken, New Jersey. 
t Present address: Department of Chemistry, Brown University, 
Providence, Rhode Island. 
1D. A. Keys, Phil. Mag. 42, 473 (1921). 
{| These gauges are now being produced commercially by the 
Cambridge Thermionic Corporation, Cambridge, Massachusetts. 
31 
extraneous signals, adequate high and low frequency 
response, minimum distortion of the pressure field, 
ruggedness, and simplicity. 
The efforts of the UERL group were directed toward 
the development of a gauge affording a practicable 
compromise among these requirements. 
Ill. SELECTION OF THE GAUGE MATERIAL 
Of the many known piezoactive crystals, those that 
have been used and investigated most extensively are 
rochelle salt, ADP, quartz, and tourmaline. More re- 
cently, crystals such as barium titanate and its various 
modifications, lithium sulfate, and certain tartrates 
have been successfully prepared and utilized. 
The most sensitive of these materials are rochelle 
salt, barium titanate, and ADP. The first two do not 
appear to be suitable for measurement of fairly large 
pressure amplitudes owing to a relaxation or hysteresis 
effect which causes them to produce a rising signal upon 
application of a step pressure. Rochelle salt and ADP 
exhibit further disadvantages in that they are not 
hydrostatically sensitive and not sufficiently rugged for 
the applications here intended. The other ‘‘synthetics” 
present various difficulties due to their solubility or the 
presence of water of crystallization. 
An extensive survey of piezoelectric activity of 
minerals has been reported by Bond.? It is interesting to 
note that after listing all the known piezoactive, natu- 
rally occurring minerals, Bond concludes that only 
quartz and tourmaline are practical for any extensive 
piezoelectric work. All the other active minerals are very 
rare, occur in the form of exceedingly small crystals, 
or are very weak mechanically. 
Quartz was rejected because of its lack of hydrostatic 
sensitivity. Because of its ruggedness, linearity, insolu- 
bility, and hydrostatic sensitivity, tourmaline appeared 
to offer most promise for the construction of small, 
simple gauges and was selected accordingly. 
IV. DESIGN AND CONSTRUCTION OF 
TOURMALINE GAUGES 
A. Basic Considerations of Design 
Since the criteria listed in Section II are not all mutu- 
ally consistent, the design of a gauge for a particular 
2W. L. Bond, Bell System Tech. J. 22, 145 (1943). 
