sta 6+20 and gage 625 at 19+00 (Figure 2). These gages are rugged and reli- 

 able, and require little maintenance except to keep tension on the cables and 

 to remove any material which may cause an electrical short between them. 

 These gages were calibrated prior to installation by creating an electrical 

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

 the voltage output. Electronic signal conditioning amplifiers are used to en- 

 sure that the output signals from the gages are within a 0- to 5-V range. 

 Gage accuracy is about 1 percent with a 0.1 percent full-scale resolution. 

 These gages are susceptible to lightning damage, but protective measures have 

 been taken to minimize such occurrences. A more complete description of the 

 gage's operational characteristics is given by Grogg (1986), 

 Waver ider buoy wave gages 



29. A Waver ider buoy gage (620) was positioned offshore 3 km from the 

 monumentation baseline (Figure 2). This gage was manufactured by the Datawell 

 Laboratory of Instrumentation, Haarlem, The Netherlands, and measures the ver- 

 tical acceleration produced by the passage of a wave. The signal is double- 

 integrated to produce a displacement signal, which is transmitted by radio to 

 an onshore receiver. The manufacturer states that wave amplitudes are correct 

 to within 3 percent of their actual value for wave frequencies between 0.065 

 and 0.5 Hz (15- to 2-sec wave periods). However, calibration curves for buoys 

 used at the FRF prior to 1983 (see Miller 1984, Miller et al. 1985 and 1986) 

 indicate that the wave heights for the combined data from 198O through 1982, 

 reported in Part V of this report, for wave periods less than 15 sec, average 

 about 7 percent less than actual values. For wave periods greater than 15 sec 

 this error increases with wave period. The manufacturer specifies the error 

 can increase to 10 percent for wave periods greater than 20 sec. Calibration 

 results show errors as large as 15 percent are possible for the very long wave 

 periods. Calibrations of buoys used during 1983 are within the manufacturer's 

 specifications. The buoys were calibrated without the use of the mooring sys- 

 tem during deployment. This occurrence may introduce additional errors of an 

 unknown magnitude. For most engineering applications, a 7 percent error is 

 tolerable; however, a correction procedure is described in Appendix A, thus 

 allowing the calibration error to be improved up to 4 percent. 



19 



