on the cables and to remove any material that may cause an electrical short 

 between them. It was calibrated prior to installation by creating an electrical short 

 between the two cables at known distances along the cable and recording the 

 voltage output. Electronic signal conditioning amplifiers are used to ensure that 

 the output signals fi^om the gauge are within a 0- to 5-V range. Manufacturer- 

 stated gauge accuracy is about 1.0 percent, with a 0.1 -percent 

 full-scale resolution; full scale is 14 m for Gauge 625. This gauge is susceptible 

 to lightning damage, but protective measiu^es have been taken to minimize such 

 occurrences. A more complete description of the gauges' operational 

 characteristics is given by Grogg (1986). 



Buoy gauge 



One Datawell Laboratory for Instrumentation (Haarlem, The Netherlands) 

 Waverider buoy gauge (Gauge 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 receiver. The manufac- 

 turer 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 gauges 



One Senso-Metrics, Incorporated (Simi Valley, CA), pressure 

 transduction gauge (Gauge 111) installed near the ocean bottom measures the 

 pressure changes produced by the passage of waves creating an output 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 

 gauge (Gauge 64 1) was installed near the ocean bottom on an instrument pile 

 under the pier at station 7+80. Calibration is similar to that performed on 

 Gauge 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. 



20 



Chapter 3 Waves 



