590 
20 
To Amplifier To Amplifier 
Water 
Surface 
Water 
Surface 
h e > 
ore ie aie charge. 
Figure 9a - Sidewise Orientation Figure 9b - Endwise Orientation 
The charge is offset from the cable, to produce The charge is in line with the end of the cable. 
lateral movement of the latter. 
Figure 9 - Orientations of Cable Relative to Charge 
in the Early Cable Tests 
they are unsheathed. In Cable D, prepared by the Precision Tube Company, the 
copper tubing is placed over the insulation by a drawing operation. The re- 
sulting hardness of the tubing cannot be removed by annealing because this 
would damage the insulation. In Cable E, prepared at the Taylor Model Basin, 
Number 24 wire covered with fiber-glass insulation is inserted into tubing 
with a wall thickness of 0.034 inch. Because the tubing in the latter cable 
can be annealed before the wire is inserted, it has the advantage of flexi- 
bility. However, since the central wire is rather loose (this cable was made 
up without wax) it is capable of motion relative to the concentric tube. Hence 
the cable signal shows high-frequency oscillations due to the vibration of the 
wire; see Figure 10b. 
To determine how much reduction in the peak voltage of Cable E could 
be effected by reducing the relative motion of the central wire, a test was 
made with a charge placed on an extension of the axis of the cable; see Figure 
9b. The distance between the immersed end of the cable and the charge was 
kept fixed. The resulting peak voltage was 2 millivolts, compared to 13 mil- 
livolts when the charge was in the position shown in Figure 9a. 
It appeared that of all the cables tested Cable E would be the most 
satisfactory for use in explosion gages, provided that it could be made in- 
sensitive to orientation. To accomplish this, it was decided to fill the 
space between the tube and the wire with wax (18). The modified cable, here- 
after called the "TMB “able," gave satisfactory results, as shown in Table 2, 
