76 



HYDROGRAPHIC MANUAL 



for the tube are not connected to the stylus 

 motor and are independent of the frequency 

 of the power source. The circuits are factory 

 adjusted for a nominal calibration velocity 

 of 800 fathoms per second. In time these 

 circuits may drift and there will be a dif- 

 ference between recorded soundings and the 

 depth shown in the scope. This feature shall 

 not be used for hydrography. 



The sounder is used with a transducer 

 designated AT-200A-UQN-1 designed to op- 

 erate at a frequency of 12 kc (see 3-105) . 



3-79 Use of multiple siylii.— When 

 sounding on the 6,000-fathom scale, sound- 

 ings cannot be scaled from the fathogram 

 with an accuracy much better than 10 fath- 

 oms. In order to extend the use of the 

 600-fathom scale, stylus belts with one or 

 two additional stylus holders can be used. 

 The holders are spaced on the belt at a dis- 

 tance equal to that between the top and 

 bottom marks on the fathogram paper, that 

 is, when the first stylus is at the 600-fathom 

 mark the second stylus is at the zero mark. 

 The extra holders do not contain keying con- 

 tacts. When more than one stylus is used, 

 it is necessary to install a thin plastic guard 

 just above the zero mark and just below the 

 600-fathom mark to prevent simultaneous 

 markings by two stylii. Since the keying 

 stylus always marks the initial pulse it is 

 sometimes difficult to scale the soundings re- 

 corded over the initial marks in the 600- to 

 700- and 1,200- to 1,300-fathom range. This 

 is particularly true when the bottom has a 

 very gradual slope. Doubling the paper speed 

 (3-78) usually solves this problem. If dif- 

 ficulty is experienced in reading the sound- 

 ings at the doubled paper speed, a cutout 

 switch may be installed and the initial trace 

 eliminated by manual operation of the switch. 



3-80 Operation of EDO-185.— Mainte- 

 nance of the EDO-185 is the responsibility 

 of qualified technicians aboard ship; how- 

 ever, unskilled personnel can be trained as 

 operators in a short time. It is advisable to 

 have a technician start the sounder and check 

 it for satisfactory operation one-half hour 

 before beginning the day's work. The op- 



erator should be trained to observe and re- 

 port indications of malfunctioning of the re- 

 corder. The initial pulse should always be 

 recorded at the zero line, or an adopted ini- 

 tial corresponding to the depth of the trans- 

 ducer. Any variation of the initial should 

 be reported and the initial adjusted in order 

 to avoid tedious application of corrections. 

 The gain should be maintained at the high- 

 est point possible without causing spurious 

 marks on the graph. If the record becomes 

 faint when good signals are received, it may 

 be caused by a coating on the platten. A 

 frequency meter is included in some installa- 

 tions. The meter should always read 60 

 cycles and variations in excess of 0.2 cycle 

 should be recorded and reported immediately. 



All servicing, adjustment, or repair shall 

 be made by qualified technicians. Operation 

 of this equipment involves the use of high 

 voltages. Operating personnel must observe 

 safety rules at all times. 



To ensure proper operation of the EDO- 

 185, a complete check of the S-201 keying 

 assembly shall be made before starting a 

 hydrographic survey. Dirty contacts in this 

 assembly may cause errors of several fath- 

 oms in the recorded soundings. A normal 

 initial mark on the fathogram does not neces- 

 sarily provide assurance that the keying 

 assembly is functioning properly. To detect 

 malfunctioning, listen carefully to the out- 

 going pulse with the headphones and the in- 

 strument operating on the 600-fathom scale. 

 The sound should be a clear, sharp "beep." 

 Check across the output to the transducer 

 with an oscilloscope. A uniform rectangular 

 pulse lasting about 15 milliseconds should be 

 produced. A daily check should be made with 

 the headphones, and a weekly check with the 

 oscilloscope. 



If the S-201 keying assembly does not 

 function properly, it should be disassembled 

 and the contacts thoroughly cleaned. Ad- 

 justment after assembly is sometimes diffi- 

 cult and time consuming and shall be ac- 

 complished by a competent technician. 



3-81 Precision Depth Recorder (PDR).— 



The Precision Depth Recorder (usually 

 shortened to (PDR) was developed jointly by 



