592 
22 
should be noted that although the time scales are different in the three rec- 
ords, the voltage scales are the same. 
The TMB cable possesses the following advantages: 
a. Compared to the unmodified Cable E, it is relatively 
insensitive to orientation. 
b. For sidewise orientation, Figure 9a, it gives a peak 
signal less than 1/3 as large as does the unmodified copper cable, 
and about 1/30 of that produced by commercial rubber-sheathed 
cables. 
c. High-frequency voltage oscillations due to vibration 
of the wire in the unwaxed copper-tube cable are eliminated; com- 
pare Figures 10b and 10c. 
d. It is very flexible, since the copper tubing remains in 
the annealed condition after the central wire is inserted. 
e. The use of copper tubing as a shield makes it easy to 
lead the gage cable into a pressure chamber for calibration. 
With rubber cable it is difficult to seal the gage inside the 
pressure chamber so that it will hold high pressure without dam- 
aging the rubber insulation. 
f. It has a relatively low dielectric absorption. Conse- 
quently, its capacitance shows a negligible change with frequency, 
as compared with variations as high as 15 per cent observed for 
rubber-sheathed cables between 150 cycles per second and 30,000 
cycles per second. 
Because of these characteristics the TMB cable appears to be better 
suited for use with underwater explosion-pressure gages than any of the others 
tested. It has been adopted for all such gages recently constructed at the 
Taylor Model Basin. 
In addition, two other features of the cable were investigated; the 
reproducibility of the voltage signal and the effect of changing the config- 
uration of the cable in the pressure field. Ina series of five detonations 
under nominally identical conditions, the peak voltage signal from the cable 
alone was found to be reproducible to within a probable deviation of 4 per 
cent. To test the effect of departure from a linear configuration, the cable 
was bent into a circle with the charge at its center. There was little change 
in the resulting cable signal. 
Further tests of the relative merits of the TMB cable and a rubber- 
sheathed cable were subsequently made at the Underwater Explosives Research 
