5323 HYDROGRAPHIC MANUAL PaGE 502 



being lifted from the paper on its return. Most of the MS instruments have one or more phases to 

 extend the depth range. 



Toroidal-shaped magnetostrictive transmitting and receiving units are employed with frequencies 

 of 16 kilocycles. These units are described in 5273 and illustrated in figure 109. For portable 

 installations the magnetostrictive units are housed in a streamlined casing, while for permanent 

 installations they are housed in water-filled tanks secured to the inner side of the steel hull of the 

 vessel. Shock excitation from the discharge of a condenser is used to excite the transmitting units. 

 The keying mechanism that brings about the condenser discharge operates in conjunction with the 

 indicating mechanism. 



All the portable instruments are operated exclusively by power from dry and storage batteries; 

 but, in addition to batteries, the permanently installed deep-water equipment requires power from 

 the ship's 110- volt d-c source for driving-motor and transmitting-unit operation. 



The recording mechanism and echo amplifier are housed in a single cast-metal cabinet. All the 

 controls necessary for operation are located on the front and side of this cabinet. 



The echo amplifier consists of two or more thermionic tubes and its input transformer is tuned 

 to the frequency of the echo signal. In the output of the amplifier a copper-oxide rectifier converts 

 the alternating current to direct current before it is applied to the recording stylus. 



Two of the MS type graphic-recording instruments used by the Coast and Geodetic Survey are 

 described in 527 and 528. 



5323. Visual- Indicating Instrument » 



The Hughes visual depth-indicating device consists of a rectangular solenoid which rotates at a 

 constant angular velocity proportional to that of sound in sea water. A soft-iron needle is mounted 

 inside the solenoid so that its axis of rotation coincides with the axis of rotation of the solenoid. A 

 pointer that moves over the calibrated depth scale is coupled to the soft-iron needle. As the solenoid 

 is energized by the impulse of the echo, the needle tends to set itself parallel to the axis of the solenoid. 

 The result is that the pointer moves to the position of the rotating solenoid at the instant the echo 

 is received. The remaining parts of the instrument are similar to the equipment previously de- 

 scribed. 



5324. Marconi Company Instruments 



Because of the affiliation between the Marconi Company of England and S.C.A.M. of France, 

 many of the echo-sounding instruments manufactured by these companies are quite similar. The 

 Marconi Company makes visual-indicating and graphic-recording instruments so nearly resembling 

 the S.C.A.M. Echometre and Electrolitic Recorder as not to warrant further description. Quartz- 

 crystal transmitting and receiving units are used similar to those already described in 531 for the 

 French instruments. 



In addition to the piezoelectric units, the Marconi Company makes use of magnetostrictive units 

 in certain other instruments. One instrument, called the "Zero to 150-fathom Navigational Equip- 

 ment," employs the Echometre visual indicator, or an electrolitic recorder, in conjunction with 

 magnetostrictive transmitting and receiving units. Another instrument for use in greater depths 

 incorporates an electrolitic recorder with magnetostrictive units designed to furnish more acoustic 

 •energy; the depth range of this instrument is from to 3,000 fathoms. 



The magnetostrictive element consists of a 5-inch core composed of a number of rectangular 

 •nickel laminations through which the magnetic flux passes, the remainder of the magnetic circuit 

 'being completed through a high-permeability nonmagnetostrictive material. The entire unit has 

 the appearance of a core-type transformer, the core of which has a few turns of wire wrapped around 

 it. The ends of the magnetostrictive core act as the emitting surfaces. The sound energy from the 

 ends of the core is directed toward the bottom by means of reflectors. This assembly is installed in a 

 water-filled tank which is fastened against the inside of the hull plates of the vessel, the sound pene- 

 trating the plates. Where increased acoustic energy is required for deep-sea sounding the hull plating 

 below the tank is cut and a thin metal plate inserted; in addition, more electric energy is supplied, 

 and fewer turns are wound around the magnetostrictive core. These magnetostrictive units are 

 •shock-excited by the discharge of a condenser. 



533. German Instruments 



The echo-sounding instruments manufactured by the Atlas Werke Company of Bremen, Germany, 

 are of the visual-indicating type and employ magnetostrictive units to transmit and receive the 



