A MOORED OCEANOGBIAPHIC DATA ACQUISITION SYSTEM 



Originally, the spar buoy was installed with only one large float, but vari- 

 able tidal currents and wind caused the spar to rotate around its mooring 

 anchor and foul its mooring line. This dual float system eliminates the ro- 

 tation of the spar due to currents and wind. Plastic pipes were installed 

 over the tether wires to prevent loops and possible fouling with the spar. 

 The lower half of the floats' mooring lines are nylon and are secured to 

 smooth, low profile dead weight anchors. Auxiliary floats were installed on 

 the nylon line to keep it off the bottom and prevent chafing. The electrical 

 signal cable is secured to the tether wire and mooring line with nylon straps. 

 The anemometer is mounted on top of the spar and the wave height sensor is 

 secured to the side of the spar. 



SUBMERGED BUOY 



The submerged buoy^ (Fig 6) , is fabricated of fiberglass and is partially 

 filled with expanded high density polyurethane to provide a positive buoyancy 

 of 2000 pounds. Thrust bearings have been installed on the buoy's mooring 

 axle to allow the buoy to head into the currents, thereby permitting the 

 instruments below it to remain fixed. Current speed and direction meters are 

 mounted below the buoy. This system is moored 25 feet below the surface with 

 a multiconductor double armored cable, the armor being the strength member. 

 Three temperature sensors are fastened to the mooring cable at 25 foot 

 intervals . 



SENSORS 



The wind speed sensor (Fig 7) is of a standard four cup design whose 

 shaft is magnetically coupled to sealed reed switches. The first wind speed 

 meters installed became inoperative after a few weeks of service due to cor- 

 rosion and salt accumulation between the shaft and bearings. Installing ny- 

 lon bearings, chrome plating the shaft and leaving .005 inch clearance be- 

 tween shaft and bearings to allow rain water to flush out salt deposits has 

 substantially reduced these problems. After several months of operation, the 

 new wind speed meter showed virtually no signs of wear or corrosion. Its 

 calibration curves show it to be substantially linear to 100 miles per hour.-^ 



The wind direction sensor is mounted directly below the wind speed meter. 

 A low torque resistive potentiometric wind direction sensor was originally 

 used, but failed after a few months of service due to excessive wear over a 

 limited section of the resistive element. Prevailing Southeast winds and 

 jitter in the vane caused the excessive wear. To overcome this problem, a 

 non-ambiguous, incremental type sensor was developed which utilizes twenty 

 magnetically actuated reed switches, thereby, giving a resolution of 18°. 

 It is oriented to a magnetic compass mounted directly below it. 



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