625 
=) Sie 
Plate 2; the spare spot on each oscillogram representing a sine wave 
oscillation of period 0.001 sec. The defleotions have been measured and 
Table 1 gives the results obtained. Graph 1 shows how the cathode ray 
deflection varies with the length of cable subjected to pressure for the 
two values of oircuit capacity. 
From either of these two curves, the cable signal per foot of cable 
can be determined. Both curves give practically the same value, and this 
can be expressed by stating that if the cable capacity were 2500yuyF, and 
no amplifier were used, the voltage produced across the cathode ray plates 
would be 00178 volts if 1 foot of cable were subjected to a pressure of 
1000 lbs./in.*. . 
(b) Test with standard cable; a P.V.C. outer covering 
A cable similar to the "standard" type but having e plyvinyl chloride 
covering instead of rubber was used to examine the variation of signal with 
pressure. Graph 2 gives the results obtained. For a cable capacity 
cireuit of 2500uuF the voltage produced across the cathode ray plates would 
thus be 0.121 volts if 1 foot of cable were subjected to a pressure of 
4000 lbs./in.?, It is interesting to note here that the commencement of 
cable signal measurements, about 30 feet of this cable Gives with the P.V.C. 
covering) was subjected to a release pressure of 1000 1bs./in.* when the 
cable was connected direct to the cathode ray plates in a circuit of 
approximately 2500 uu F capacity, a deflection of about + mm. was obtained. 
This figure is now confirmed of course by the more elaborate results 
obtained later and given above. (C,.R.0. film sensitivity = 15.85 volts/mm). 
(c) Test with Admiralty Pattern rubber covered cable. 
Primarily with the object of obtaining evidence as to the cause of 
cable signal, and also with a view to determining the signal given by such 
rubber covered cable as were used by former workers with large piezo- 
eleotric gauges, \dmiralty Pattern 1888 cable was next examined. This 
consists of 19 strands of tinned copper wire, each strand being 0.018" in 
diameter, bound with a tough rubber sheath to an overall diameter of 
approximately 0.35"; a photograph of this cable appears on Plate 1. 
The results obtained showed that under the same conditions of 
subjecting 1 foot of cable to a pressure of 1000 lbs./in.* in a cirouit of 
capacity 2500 uF. the voltage developed across the plates of the cathode 
ray tube would be 0.040 volts, but the direotion of the cable signal was 
opposite to that obtained for the two telocothene cables. 
The cenclusions to be drawn fron these tests and the curves 
illustrated in Graphs 1 and 2 are that the cable signal voltage is 
(1) directly proportional to the pressure to which the cable is subjeoted, 
and (2) directly proportional to the length of cable subjected to pressure. 
In the case of the cable developed for use with piezo-electric gauges at 
Admiralty Undex Works, the cable signal is quite large, in the opposite 
direction to and about 4 times preater than that of one of the standard 
Admiralty Cables, Admiralty Pattern 1888. Moreover the oatle signal for 
the "standard cable" is in the same direction and nearly i4 times that of 
an identical cable where the tough rubber sheath has been replaced by a 
polyvinyl chloride covering. 
THE MAGNITUDE OF CABLE SIGNAL. 
At this stago it is necessary to compare the effeot of the "standard" 
cable signal with that of the gauge Signal. The piezo-electrio gauges 
being developed at Admiralty Undex Works are of three types, (4) the large 
twoeply type of dimensions 40 oms. x 4 cms. x 1 em.; (ii) the medium two-ply 
type 1" in diameter, 3" thick; and (iii) the small two-ply type $" in 
diameter, =" thick. Eight gauges of type (i) have been completed, each 
fitted with 250 yards of "standard" cable, but modified to reduce cable 
signal eeeee 
