A MOORED OCEANOGRAPHIC DATA ACQUISITION SYSTEM 



The wave height sensor is a sixteen foot staff utilizing a floating mag- 

 net in a slotted aluminum tube that actuates series connected sealed reed 

 switches (Fig 8) . The reed switches are housed in a sealed oil-filled poly- 

 vinyl chloride pipe that is attached to the aluminum tube. This design eli- 

 minates the objectional features of residual resistance in exposed resistance 

 type staffs and the aluminum tube prevents jamming of the float. The staff 

 is secured to the side of the buoy with 8 feet of its length exposed above 

 water. The reed switches are mounted on 3 inch centers so that waves from 

 six inches to sixteen feet can be monitored. The entire wave staff is 

 painted with an organic tin base antifouling paint. 



The current speed meter (Fig 9) , suspended six feet below the submerged 

 buoy, is a Savonius rotor type of molded plastic supported in an aluminum 

 housing which is magnetically coupled to sealed reed switches. It has been 

 calibrated to five knots. The current direction meter, mounted above the 

 rotor, is magnetically coupled to a 360° resistive potentiometer whose shaft 

 is magnetically linked to a magnetic compass. Tungsten bearings and anti- 

 fouling paint were used to give maximum life to the instruments. Resolution 

 of the current speed and direction meters are .1 knot and 20° respectively.' 



To measure ambient noise, two preamplifier-hydrophone assemblies are 

 mounted on the bottom. Because of the high signal levels coming from the 

 commutator package to the laboratory, separate cables connect the hydrophones 

 to shore in order to avoid cross talk. They are placed two hundred feet from 

 the buoys to keep buoy generated noise from masking the ambient noise. Fre- 

 quency response of the hydrophone-prearaplif ier-cable system is 20 cps to 

 2000 cps ± 1 dB. The sensitivity of the hydrophone is -92 dBV|ab and the 

 preamplifiers have a gain of 40 dB. 



SPLICES AND SEALS 



The commutator package is a bottom mounted aluminum cylinder weighted 

 down with concrete ballast (Fig 10). To afford a more flexible system and 

 prevent total failure if one or more of the connecting cables floods, a 

 separate bulkhead connector and plug is used for each sensor's output. Com- 

 mercially available waterproof plugs and bulkhead connectors are used at all 

 cable entrances, both above and below water. -^ All splices were hand taped 

 with self amalgamating polyethylene or neoprene tape and antihosing stops 

 were installed in each splice. 



INSTALLATION 



To install this system, a careful survey was made by SCUBA divers to 

 check water depth and topography. Anchor, commutator package and cable posi- 

 tions were carefully marked and buoyed. A converted 90 ton "T" boat was 



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