INFLUENCE OF A HIGH HYDROSTATIC PRESSURE ENVIRONMENT 
ON ELECTRONIC COMPONENTS 
by CHESTER L. BUCHANAN, Branch Head = 
and MATTHEW FLATO, Electronics Section Head 
Sonar Systems Branch, Sound Division 
U.S. Naval Research Laboratory 
Washington, D.C, 
ABSTRACT 
The rapidly expanding field of Oceano- 
graphic Instrumentation portends a large in- 
crease in the use of electronic instrumentation 
in various forms of deep ocean probes, One 
part of the oceanology program at USNRL is 
directed toward the development of such in- 
struments, 
Two approaches toward this development 
are available: The equipment can be sealed in 
rigid pressure-proof capsules with pressure- 
proof seals, or the equipment can be made of 
components which are inherently capable of 
operating satisfactorily under the environment- 
al pressure, The latter approach is attractive 
because of the probable savings in weight and 
cost. To this end, a series of commonly used 
electronic components have ‘been tested in an 
oil bath under hydrostatic pressures up to 
10,000 psig. Components of each type tested 
have been found which will operate satisfactor- 
ily at all pressures up to 10,000 psig. Diodes, 
transistors and even vacuum tubes have been 
found which operate at this high pressure, 
Entire circuits capable of operation under 
10,000 psig have been built from readily 
available components. 
INTRODUCTION 
It is a certainty that the rising tempo in 
Oceanographic Research will require an in- 
crease in the use of electronic instrumentation 
with various forms of deep sea probes. In- 
struments designed for deep submergence must 
be constructed to withstand the pressure expe- 
rienced at great depths, One part of the ocean- 
ographic instrumentation program at the U. S. 
Naval Research Laboratory is directed toward 
the development of packages for instruments 
whose electronic components are exposed to 
hydrostatic environments equivalent to more 
119 
than four miles submergence in the ocean. 
The initial phase of this study was exploratory; 
the objective was two-fold, to gain familiarity 
with techniques for testing components under 
high hydrostatic pressure and to determine the 
magnitude of the difficulties to be expected 
while operating equipment under such condi- 
tions, Initially several approaches are avail- 
able: the equipment can be constructed of com- 
ponents which are inherently capable of oper- 
ating satisfactorily under the environmental 
pressure, or the equipment can be encapsu- 
lated in plastic which fully protects the com- 
ponents, As an example of the results to be 
expected from the first mentioned approach, 
the 'velocimeter", in which electronic circuit 
components weigh less than four ounces, re- 
quires a housing that weighs 25 pounds to pro- 
tect the components at a pressure of 10, 000 
psi. This high package to circuit weight ratio 
is typical of that to be expected from this 
practice, The probable saving in weight and 
cost, which can be expected from the latter 
two approaches, makes the further study of 
these techniques attractive, 
Several classes of electronic components 
have been tested in laboratory tanks (Figures 
1 and 2) which were designed to apply high 
hydrostatic pressure, 
RESISTORS 
The first class of components tested was 
resistors, How the various types reacted 
under hydrostatic pressure may be compared 
in Figure 2, The resistance of those manu- 
factured by depositing either carbon film or 
tin oxide on glass rods was not changed by the 
application of pressure; the behavior of these 
two types of resistors strongly suggests their 
use in critical circuits, 
