3. EQUIPMENT AND INSTRUMENTS 



87 



used with the EDO-255, but one transducer 

 operation is most common. The transducer 

 acts alternately as a sending and receiving 

 unit. This transducer has a beam width of 

 20 degrees which is symmetrical about its 

 principal axis. This narrow beam provides 

 a high sound conversion efficiency and makes 

 for more accurate sounding. 



A new type transducer is being developed 

 for the 255 echo sounder. It is also a Bariiim 

 Titanate unit, but is made up of molded 

 blocks of this material. The blocks radiate 

 directly from one face to the sea water. This 

 transducer is capable of producing many 

 times as much sound energy as the one now 

 in use. 



3-105 The EDO-185 transducer.— The 



deep water echo sounder, Type UQN, uses 

 a transducer which employs an array of 

 45-degree, Z-cut ammonium dihydrogen phos- 

 phate (ADP) crystals. The dimensions and 

 arrangement of the crystals and a monel 

 backing plate produce maximum energy 

 transfer (resonance) at about 12 kilocycles. 

 The mechanically active surfaces of the crys- 

 tal array face downward when the trans- 

 ducer is installed. When energized, the vi- 

 bratory motion of the crystals is transferred 

 to the water through dehydrated de-aerated 

 castor oil and an acoustically transparent 

 window. The beam has a width of 64 de- 

 grees which is symmetrical about the prin- 

 cipal axis. This wide beam is caused by the 

 relatively low frequency even though the 

 transducer has a comparatively large diam- 

 eter of 10 inches. 



One transducer is used to transmit and 

 receive. The power delivered to the trans- 

 ducer is about 800 watts with a pulse length 

 which varies from 2 to 150 milliseconds de- 

 pending on the sounding scale being used. 

 The efficient transducer coupled with low fre- 

 quency and large excitation power make it 

 possible to sound in the deepest water with 

 the UQN. 



3-106 High frequency transducers. — Two 



high frequency echo sounders are being used 

 by the Bureau for limited and special sur- 

 veys. These are the Raytheon DE 119 and 



the Bloodworth type ES 130. Their trans- 

 ducers are so similar that a single descrip- 

 tion will suffice for both. The acoustic ele- 

 ment is a thin wafer of Barium Titanate 

 embedded in a plastic housing. Their metal 

 electrodes are secured to opposite faces which 

 couple the electrical and mechanical parts of 

 the systems. Radiation is from one surface 

 to the bottom. These transducers are trans- 

 mitter excited at 200 kilocycles per second. 

 They have a diameter of 3 inches and a 

 beam width of 6 to 8 degrees. 



3-107 Care of transducers. — Transducers 

 are sturdy devices which require only pe- 

 riodic inspection and occasional servicing. 

 They should not be subjected to harsh phy- 

 sical shocks which may damage the housing 

 or the interior elements. 



Maintenance of magnetostriction type 

 transducers consists essentially of cleaning 

 the exposed side of the laminations. This 

 surface should be wire-brushed to remove 

 barnacles or other types of marine growth. 

 In some installations the transducer is housed 

 in a castor oil-filled sea chest. In this case 

 the only maintenance required is to check 

 the oil level about once every two to three 

 months and see that the chest is always full. 

 Only an approved oil furnished for this pur- 

 pose shall be used. Other oils may damage 

 the insulation on the wires. 



Most electrostatic transducers have the 

 active element emersed in a castor oil bath 

 and the housing must be kept filled with an 

 approved grade of oil. In some of the new 

 transducers coming into use the active ele- 

 ment (barium titinate) is placed in a square 

 housing which is then filled with a plastic 

 material called epoxy. The exposed surface 

 of this type of transducer should be cleaned 

 with a non-metallic, non-abrasive brush. 



The electrical insulation leakage and re- 

 sistance of the connections for all types of 

 transducers should be examined at least once 

 a month while the units are in service. The 

 leakage is best checked with a 500-volt meg- 

 ger. The wire windings on 808 transducers 

 will deteriorate with time or may be dam- 

 aged. When the megger indicates leakage, 



