UNDERWATER WEATHER STATION 375 



Data Acquisition System 



A system of analog and digital recorders, along with necessary amplifiers, digitizers, and 

 logic control units, was located in the benthic control center near the telemetry receiving ter- 

 minal equipment. A 12-channel chart recorder monitored analog readouts from the underwater 

 weather station and from the pier end anemometer. A separate chart recorder monitored an 

 analog conversion of the output of the pier end digital wave staff. The chart speed of the latter 

 recorder could be changed as desired to obtain short records of wave profile (Fig. 140), as 

 well as long-term records of lower frequency phenomena such as tides and shelf seiche. 



290 

 200 



_l I I I l_J I I 1 I 1 U- 



_J I I I I L_ 



150 

 TIME IN SEC 



Fig. 140. Wave record from the digital wave staff mounted on the end of the Scripps In- 

 stitution of Oceanography Pier. Record begins at 1200 PST, Oct. 6, 1965, and is repre- 

 sentative of waves contributing to the spectrum in Fig. 144. 



The telemetry receiving equipment monitored the output of the analog-to-digital converter 

 in Sealab and recorded the information incrementally on magnetic tape. Data which were telem- 

 etered direct (without conversion) were channeled into a data-acquisition system (DAS) for 

 sampling at shorter time intervals. Plug-in, printed-circuit logic boards were used in the ac- 

 quisition system to digitize the sampled data, to store in memory banks in binary form infor- 

 mation from all input channels, and to present the information in increments to a high-speed 

 magnetic tape recorder for permanent storage. The tape record was in standard IBM format 

 and could be programmed directly into a computer for analysis. 



INSTALLATION OF UNDERWATER WEATHER STATION 



The underwater station platform was lowered to the sea floor from the staging vessel 

 Berkone on the evening of Sept. 4, 1965. The platform in its lowering position (Fig. 141) con- 

 sisted of a central 1/2-in. -thick steel plate, 32 x 32 in. on a side, to which were welded four 

 leg guides and two instrument mounting brackets. Other components, including the taut wire 

 and its float and the flotation equipment, were lashed to the platform between the four anchor 

 legs, which in their lowering position form a "teepee" structure. Once on the bottom, the plat- 

 form was located in the turbid water by two divers using a 25-40 kc hand-held sonar. A 37-kc 

 "pinger" attached to the platform provided a target for the sonar. 



The underwater weather station was diver-oriented in its design. It was intended that it be 

 easily moved by two divers after inflating four rubber tubes to give it neutral buoyancy. The 

 tubes were inflated by bleeding air from a scuba bottle into holes cut in the tubes near their 

 point of attachment. This arrangement provided the necessary safety control to prevent over- 

 inflation and excess positive buoyancy. The air in the tubes could be spilled instantly by squeez- 

 ing the tube. After inflating the tubes, the platform was transported 165 ft to the installation 

 site by two divers. The site (Fig. 138, position 3), which had been determined previously dur- 

 ing reconnaissance dives, was on a slight rise where currents would be more typical of the 

 area than in the valley at the Sealab site. The platform was firmly anchored in place by four 

 anchor pounded legs into the bottom. The taut-wire mooring was then released from the plat- 

 form and assumed its vertical position, maintained in a taut position by the 75-pound positive 

 buoyancy of the float. At the end of the 45-day Sealab project, all of the underwater weather 

 station sensors were attached to the taut-wire mooring, which was then released from the 

 platform and retrieved on the surface. 



