gages are within a 0- to 5-V range.' Manufacturer-stated gage accuracy is about 1.0 percent, with a 

 O.l^ercent full-scale resolution; full scale is 14 m for Gage 625 and 8.2 m for Gage 645. These 

 gages are suscq)tible to lightoing damage, but protective measures have been taken to minimize such 

 occurrences. A more complete description of the gages' operational diaracteristics is given by Grogg 

 (1986). Gage 645 failed in May 1992 and was replaced by a pressure gage (Gage 641) mounted at 

 the same location m November 1992. 



Buoy gage 



One Datawell Laboratory for Instrumentation (Haarlem, The Netherlands), Waverider buoy gage 

 (Gage 630) measures the vertical acceleration produced by the passage of a wave. The acceleration 

 signal is double-integrated to produce a displacement signal transmitted by radio to an onshore re- 

 ceiver. The manufacturer stated that wave amplitudes are correct to within 3 percent of their actual 

 value for wave frequencies between 0.065 and 0.500 Hz (corresponding to 15 to 2 sec wave periods). 

 The manufacturer also specified that the error gradually increased to 10 percent for wave periods in 

 excess of 20 sec. The results in this report were not corrected for the manufacturer's specified 

 amplitude errors. However, the buoy was calibrated semiannually to ensure that it was within the 

 manufacturer's specification. 



Pressure gages 



One Senso-Metrics, Incorporated (Simi Valley, CA), pressure transduction gage (Gage HI) in- 

 stalled near the ocean bottom measures the pressure changes produced by the passage of waves creat- 

 ing an ou^ut signal that is linear and proportional to pressure when operated within its design limits, 

 Predeployment and postdeployment calibrations are performed at the FRF using a static deadweight 

 tester. The sensor's range is to 25 psi (equivalent to to 17 m of seawater) above atmospheric 

 pressure with a manufacturer-stated accuracy of +.0.25 percent. Copper scouring pads are installed at 

 the sensor's diaphragm to reduce biological fouling, and the system is periodically cleaned by divers. 



One Paroscientific, Incorporated (Redmond, WA), pressure transduction gage (Gage 641) installed 

 near ocean bottom on an instrument pile under the pier at station 7+80. Calibration is similar to that 

 performed on Gage 111. The sensor's range is to 45 psia (equivalent to to 30 m of seawater) 

 with a manufacturer-stated accuracy of +.0.01 percent. A perforated copper/nickel plate protects the 

 sensor's diaphragm from biological fouling, and the system is periodically cleaned by divers. 



Digital Data Analysis and Summarization 



The data were collected, analyzed, and stored on optical disk using the FRF's VAX computer. 

 Data sets were normally collected every 6 hr. During storms, the collection was at 3-hr intervals. 

 For each gage, a data set consisted of four contiguous records of 4,096 points recorded at 0.5 Hz 

 (approximately 34 min long), for a total of 2 hr and 16 min. Analysis-was performed on individual 

 34-min records. 



The analysis program computes the first moment (mean) and the second moment about the mean 

 (variance) and then edits the data by checking for "jumps," "spikes," and points exceeding the voltage 

 limit of the gage. A jump is definal as a data value greater than five standard deviations from the 

 previous data value, whereas a spike is a data value more than five standard deviations from the 



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