Efficient handling of the large volume of data acquired from an array 

 of sensors can be accomplished only by modern computer techniques. Computer 

 programs, such as "BOMM" (Bui lard, Oglebay, Munk, and Miller, 1966)*, enable 

 complex time series to be rapidly manipulated and printed-out in the basic 

 form of power spectra and cross-spectra. Such presentations allow the 

 investigator to determine the principal energy modes in a given wave type 

 and the correlation between these modes and those of associated phenomena. 



The above considerations led to the design of a multi-purpose data 

 acquisition system for field and laboratory instrumentation of the nearshore 

 environment. The design of the data acquisition system (DAS) and some of 

 its special sensors, together with a few of the field and laboratory uses, 

 are described in the following sections. 



Section II. ELECTRONIC COMPONENTS 



The data acquisition system was designed to accept signals from a 

 variety of instruments, convert these signals to useful data and record 

 these data in forms amenable for processing by an electronic computer. 

 The acquisition system was constructed of solid-state logic components on 

 printed circuit boards. Recent production techniques have made \t possible 

 to obtain these boards as "off-the-shelf" items in most of the needed con- 

 figurations. The acquisition system also has an instantaneous analog 

 print-out on a paper chart so that channels can be monitored before and 

 during recording to give visual indication of sensor performance. Also, 

 the binary data entered on the magnetic tape can be step-scanned on visual 

 lights mounted on the panel to ensure that correct sensor output is printed 

 on the tape. Experience indicates that analog monitoring and visual display 

 of tape entry are valuable assets to a data acquisition system. 



Two portable racks serve to mount the entire system (Figure 1). One 

 rack houses the electronic logic equipment and associated power regulators. 

 The other rack contains recording equipment and storage batteries. The 

 batteries are held by a pivoted carrier which maintains an upright position 

 at all times. When being transported, the racks are tilted backward on 

 their axles and rolled on rubber tires similar to the action of two-wheeled 

 handcarts. The portable equipment racks are 52 inches high, 29 inches wide, 

 and 24 inches deep. These are over-all dimensions, including the wheels 

 and the lifting ring mounted on top. The logic equipment rack weighs 120 

 pounds and the power supply, with storage batteries, weighs 145 pounds. 

 Power for the equipment may be obtained from the storage batteries or from 

 a 60-cycle power line. 



Neoprene-jacketed, 250-foot four-conductor cables connect remote 

 sensors to the DAS. Mated underwater connectors are molded to the ends 

 and may be coupled for operation at greater distances. Shorter cables 

 are used in the laboratory, but otherwise the installation of the system 

 is the same there as in the field (Figure 2). 



^Notations refer to LITERATURE CITED on page 35. 



