INTRODUCTION TO SONAR 



OPERATION 



When you place the cannister in the launch 

 tube, a watertight electrical connection is formed 

 between the probe and the recorder, causing the 

 recorder to nin for 2 seconds. This action sets 

 the automatic starting circuits, which are acti- 

 vated when the probe hits the water. The probe 

 is held in position by a pin protruding from the 

 launcher. Pulling the pin permits the probe to 

 fall free of the cannister, into the water. (The 

 cannister remains in the launcher.) As the 

 probe starts its free fall, the wire conamences 

 unreeling from the probe and from the cannister. 

 This double unreeling action allows the probe to 

 sink straight down, and permits the ship to 

 proceed imhindered. 



When the probe strilies the water, an electrode 

 triggers the recorder. The thermistor transmits 

 temperature changes to the recorder, where they 

 are plotted on the strip chart by a stylus. At a 

 depth of 1500 feet, the probe's wire is exhausted 

 and the recorder stops. A complete readout is 

 obtained in 90 seconds from time of launch. 

 Temperature range of the probe is 28°F to 96°F, 

 with an accuracy of 0.4°F. Depth accuracy is 

 2 percent or 15 feet, whichever is greater. 



Figure 5-27 shows a representative tem- 

 perature-depth profile. Only 6 inches of chart 

 paper are needed for each 1500-foot drop. Pres- 

 ent plans call for the fleet to be completely 

 equipped with the XBT system within 2 

 years. 



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