CHAPTER R 



SONAR PINGER 



R-1 General. — The Sonar pinger is a battery- 

 powered, automatic cycling, submersible sound 

 generator unit. It is used for positioning ocean- 

 ographic equipment within measured distances 

 of the ocean floor. At the U.S. Naval Oceano- 

 graphic Office, the Sonar pinger has been used 

 successfully in underwater photography (chap- 

 ter N) and Nansen cast operations (fig. R-1). 

 The pinger transmits sonar pulses at precisely 

 timed intei-vals. As the pinger is lowered toward 

 the bottom, the transmitted pings are received 

 on a sonar receiver (hydrophone, etc.) and dis- 

 played on a monitor (strip chart recorder, 

 oscilloscope, etc.) to produce a continuous visual 

 record of the pinger-to-bottom distance. Since 

 each somid pulse (pii'g) is transmitted directly 

 to the sliip and also is reflected by the bottom 

 back to the ship, the interval between the time 

 the direct and the reflected pings are received is 



Tdif — 



2D 



D = 



V T,u 



V 



where D = pinger-to-botton distance (feet) 

 V = velocity of sound in water 



(feet/second) 

 Tdt t = time interval between direct and 

 reflected signals (seconds) 

 For example, if the pinger is 1,250 feet above 

 the bottom and velocity of soimd in water is 

 assumed to be approximately 5,000 feet per sec- 

 ond, the reflected ping will be received one-half 

 second after the direct ping ; 



Tdit 



2 X 1250 



5000 



.5 seconds 



likewise, a 2 millisecond difference would indi- 

 cate a distance of 5 feet above the bottom 



D = 



5000 X .002 



= 5 feet 



(see fig. R-2). 



R-2 Description of the Sonar Pinger. — The 



Sonar pinger described here is the Edgerton, 

 Germeshausen, and Grier (EG&G), Mai-k 1, 

 Sonar Pinger. Other types are available and 

 have been used by the Naval Oceanographic 

 Office. The Sonar pinger is composed of thi-eo 

 main subassemblies: Driver, pulse transformer, 



Figure R-1. 



Sonar pinger replaces weight on 

 Nansen cast. 



and transducer. The driver generates an electri- 

 cal pulse once every second; the pulse trans- 

 former steps up the voltage of the pulse ; and the 

 transducer converts the high-voltage electrical 

 pulse into a high intensity 12 KHz sound. Tlie 

 pinger driver disassembled is shown in figure 

 R-3. It consists of main driver circuitry, battery, 

 end caps, and driver housing. The pulse trans- 

 former is shown in figure R-l. It consists of two 

 windings housed in a rubber-stoppered clear 

 plastic tube filled with transformer oil. The 

 transducer is shown in figure R-5 ; it contains 



R-1 



