712 ; 
Os 
A rather detailed theory has been presented for the action of this gauge 
[7,9] and its reproducibility has been summarized [8]. However, while it 
is possible to calculate the response of the gauge from a knowm pressure 
time curve, it is not possible to determine the form of a pressure—time 
curve from the gauge response. Deformations of the copper spheres can be 
transformed to values for peak pressure provided the form of the pressure- 
time curve is previously knovm [10]. 
(iii) The Modugno gauge. The Bureau of Ships has developed a diaphragm 
type of gauge knovm as the Modugno gauge [11]. The effective diaphragm 
diameter is 1 in., and the diaphragm may be of various materials and thick 
nesses. Those used at UERL were either of approximately 0.065—in. copper 
or 0.050-in. thick cold-rolled steel. Comparison of the maximum deflection 
of these plates after being subjected to an explosive shock wave gave the 
relative effectiveness of the explosives, For large charges these gauges 
measured approximately peak pressure, having a somewhat shorter action time 
than the UERL diaphragm gauge but longer than the NOL ball-crusher gauge. 
The theory for these gauges has not been worked out to allow a computation 
of peak pressure from the gauge deflection, even when the form of the pres— 
sure-time curve is known, nor a calculation of the maximum deflection from 
a known pressurc—time curvce 
(iv) Hilliar-type gauges. Mcchanical gauges that integrate the 
pressure-time curve to give the impulse in the shock wave have been de- 
signed following the principles laid down by Hilliar [12]. In this type 
of gauge the water transfers its impulse to a freely moving piston which 
at the end of its travel strikes a copper cylinder or copper sphere, and 
from the deformation of the cylinder or sphere the energy of the moving 
piston at the time of impact can be calculated. From this energy and the 
dimensions of the gauge the total impulse imparted to the piston by the 
shock wave may be determined, as well as the travel time of the piston be- 
fore striking the copper cylinder or sphere (equivalent to the time of inte- 
gration over the pressure=time curve). 
(1) The improved Hilliar gauge. A modification by Hartmann of the 
original Hilliar. gauge incorporated seven pistons of different sizes and 
travel times into the same gauge body [13]. One of the pistons has zero 
travel distance since it is in contact with a copper sphere (essentially 
the same as a ballecrusher gauge). From the gauge dimensions and cylinder 
deformations the average pressure of the water shock wave during different 
time intcrvals may he calculated, and by plotting these average pressures 
against time a pressurc-time curve may be drawn. While this gauge is some~ 
what difficult to assemble and operate, and the calculations necessary to 
obtain a pressure-time curve are rather lengthy, it is possible to obtain 
a qualitative idea of such a curve without the use of electronic equipment. 
(2) The Hartmann momentum gauge. A Hilliar type of gauge using a 
single piston of large mass with only a small area exposed to the shock wave, 
will measure the impulse over the major portion of the pressure—time curve. 
This gauge is much simpler to assemble and operate than the improved Hilliar 
gauge mentioned above, and the calculations of the "total momentum" may be 
made by reference to a graph of impulse versus deformation. However, it 
daes not give any information regarding the form of the pressure-time curvee 
