odically. .Any rope fibers, grass, or biological 

 growth should be removed from the impeller 

 and impeller bearing, and swivels, electrical 

 and suspension cables, and ground tackle should 

 be checked. Wlien the operation is completed, 

 meters should l>e rinsed with fresh water. Ex- 

 tensive repairs in the field to the interior mech- 

 anism and impeller mount of the meter must 

 be undertaken with caution because calibration 

 data for meters are determined by preset im- 

 peller response and magnetic linkage. 



M-18 The Woods Hole Oceanographic In- 

 stitute (WHOI) (Richardson) Current 

 Meter. — The operation of the Geodyne Woods 

 Hole Oceanographic Institute (WHOI) (Rich- 

 ardson) current meter is described in this sec- 

 tion of the current meter chapter. Model A-101 

 of the current meter is used by the Naval Ocean- 

 ographic Office at the present time (fig. M-12). 

 This self-contained digital-film-recording 

 current meter measures current speed from 0.05 

 to 5 knots and current direction within dzlO°. 

 The data are recorded photographically at 

 sampling intervals controlled by an internal 

 mechanism, and as many as 4,500 sets of obser- 

 vations can lie recorded on a 100-foot roll of 

 film. The current meter may be programmed to 

 operate for a period of several days or several 

 months, depending on the frequency of the ob- 

 servations. The recording mechanism is battery 

 powered, and the meter is constructed to with- 

 stand pressures encountered at water depths of 

 5,000 meters. Figure M-13 shows the location of 

 the main components of the current meter. The 

 intelligence from the sensing devices (rotor, 

 vane, inclinometer, compass, and timing de- 

 vices) is transmitted as light through optical 

 fibers to the field of view of the camera. These 

 light pipes are referred to as channels. A timing 

 device activates the light circuits, causing the 

 various channels in the field of view to flash and 

 be photographed as a row of dots. The meter 

 can be programmed to operate continuously or 

 at predetermined intervals. Wlien operating on 

 Interval^ the meter is activated one to 12 times 

 per hour for a 50-second recording period, de- 

 pending on the cam installed on the time mech- 

 anism. The following instructions are presented 

 for guidance in operating tlie meter. 



M-19 Operating the Current Meter. — Be- 

 fore operating the current meter, the battery 

 should be checked, fresh film should be loaded, 

 and the instrument should be inspected care- 

 fully. A suggested format for a Geodyne current 

 meter checkout record is presented as figure 

 M-14. Check each item on the sheet as t\\e> in- 

 spection or installation is completed. In addi- 

 tion, the manufacturer's instruction manual 

 "TM 66-61 (Rev. 9-1-66), Instruction and 

 Maintenance Manual Model A-101 Film Re- 



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Figure M-12. Geodyne model A-101 current meter. 



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M-10 



Change 1—1970 



