over, monitoring assures maintenance of opti- 

 mum sensitivity of the recorder amplifier, which 

 is shghtly sensitive to supply voltage. All 

 components of the power supply and the instru- 

 ment side of the isolation transformer should 

 be insulated from the ship. 



9-5 Signal Input Leads. — The signal input 

 leads connect the overside cable and electrodes 

 to the recording potentiometer. They should 

 be shielded and insulated from the ship. 

 Grounding is not often necessary, but when 

 it is, the safest ground is the first electrode on 

 the overside cable. 



9-6 Recording Potentiometer. — The po- 

 tentiometer component is a recorder having a 

 2-second pen movement, and K-inch-per-minute 

 basic strip-chart speed. The upper part of the 

 instrument scale and the strip chart is calibrated 

 in centimeters per second and the lower part 

 in knots. A set of the ship to port is indicated 

 to the left and starboard set to the right of the 

 instrument zero at the center of the scale. 



9-7 The Cable. — The primary function of 

 the cable is to bring aboard a signal from far 

 enough astern to be unaffected by the ship's 

 magnetic field. The cable may tow in the 

 wake, for turbulence there is usually too small 

 and rapid to be resolved. But it is easier on 

 the cable and better practice to tow it from the 

 end of a boom similar to that used for the 

 bathythermograph. The clearance between the 

 ship and tow point should be sufficient to allow 

 the cable to pass clear of the stern even during 

 rapid turns. An outhaul to the end of the boom 

 permits convenient handling in streaming and 

 retrieving the cable when underway. In stream- 

 ing the cable, it is necessary to avoid kinks and 

 to keep the cable clear of the screw. 



9-8 Cable Connections. — Cable connections 

 to the recorder should be made according to 

 the following convention for the northern 

 magnetic hemisphere: the conductor leading 

 to the more distant electrode is connected to 

 the input terminal which is made positive and 

 gives a right-hand deflection of the pen. This 

 convention allows the observer facing the 

 recorder to see the pen on the same side of zero 

 as the direction toward which the ship is being 

 set. The connections must be reversed in the 

 southern magnetic hemisphere to have the 

 same convention apply. 



9-9 Electrodes. — The electrodes have been 

 specially lagged in order to withstand repeated 

 changes of salinity and temperature. Allow 

 at least 30 minutes wetting time when first 

 towing 'jhe electrodes. Once wetted, the elec- 

 trodes should respond without delay even 



though they may have been on deck several 

 hours. 



9-10 Spare Parts Needed for the GEK.— 



The following spare parts are needed to operate 

 and maintain the GEK. 



1. Spare cable with electrodes. 



2. Electronic service kit with a spare set of 

 electron tubes for servicing the amplifier. 



3. Spare 1.5-volt dry cells. ' 



4. Spare glass pen with stopper and cleaning 

 wire. 



5. Bottle of red recorder ink. 



6. Spare strip-chart rolls. 



7. Instruction Manual, "Directions for 

 Speedomax Type-G Recorders." 



9-11 Tools Needed for the GEK.— For nor- 

 mal operations, a medium-size screwdriver and a 

 pen cleaner are all that ordinarily are needed . 



9-12 GEK Models. — Navy survey ships 

 have two models of the GEK in use. The earlier 

 type was developed and constructed at the 

 Woods Hole Oceanographic Institution and is 

 referred to as the WHOI Model. The later 

 type is commercially made and is called GEK 

 Model V. Although the two models operate in 

 almost the same manner, there are minor 

 differences in locations and arrangements of 

 operating switches and dials. The GEK Model 

 V is more compact than the earlier WHOI 

 Model. Both use Speedomax Type-G Recorders. 

 Operating and maintenance manuals for this type 

 of recorder are supplied by the manufacturer 

 (fig. 9-1). 



9-13 OPERATING THE GEK MODEL 

 V. — Operation of the GEK .Model V is carried 

 out in the following manner. 



9-14 Stream the Electrodes. — Rig out the 

 boom and stream the electrodes. If they have 

 not been used for several days, allow 30 minutes 

 for wetting. Turn all switches on the panel of 

 the GEK recorder to OFF (DOWN) position. 

 Plug in the electrodes at the input terminals, 

 and turn on the 110 AC power supply. 



9-15 Main Power.— Turn main" POWER 

 switch to ON position. 



9-16 Paper Motor.— Move PAPER MOTOR 

 switch inside the recorder door to ON position. 



9-17 Semiautomatic Current Adjuster. — 

 After 1 minute of power-on, turn the SEMI- 

 AUTOMATIC CURRENT ADJUSTOR 

 (small knob to left of the strip chart in the re- 

 corder) clockwise for an instant and repeat 

 until the recorder pen does not respond. The 

 pen should indicate zero; i. e., lie at the center 

 of the chart paper. 



9-18 Sensitivity Control.— Turn the SEN- 

 SITIVITY CONTROL (knob marked X in 



H. O. 607 



