PART III: INSTRUMENTATION 



20. This section identifies the instruments used for long-term monitor- 

 ing of oceanographic and meteorological conditions and briefly describes their 

 design, operation, and location. More detailed explanations can be found in 

 Miller (1980). Equipment (i.e., the surveying system) used for collecting 

 other types of data is discussed in Part IV. 



Wave Gages 



Baylor wave staff gages 



21. Two parallel cable inductance wave gages, manufactured by the 

 Baylor Company, Houston, Tex. , were mounted on the FRF pier, one at sta 6+20 

 and one at 19+00 (Figure 2) . These rugged and reliable gages required little 

 maintenance except to keep tension on the cables and to remove any material 

 which could have caused an electrical short circuit between the cables. They 

 were calibrated prior to installation by placing an electrical short between 

 the two cables at known distances along the cables and noting the voltage 

 output. In the field, electronic signal conditioning amplifiers were used to 

 ensure that the output signals from the gages were within a 0- to 5-V range. 

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

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

 been taken to minimize such occurrences. 



Waverider buoy wave gages 



22. Two Waverider buoy gages were positioned 0.6 and 3 km offshore at 

 the FRF (Figure 2). These gages, manufactured by the Datawell Laboratory for 

 Instrumentation, Haarlem, Netherlands, measured the vertical acceleration 

 produced by the passage of a wave. The signal was doubly integrated to pro- 

 duce a displacement signal, which was transmitted by radio to an onshore 

 receiver. The manufacturer stated 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 indicated that the wave heights reported in Part V of this report for wave 

 periods less than 15 sec averaged about 5 percent less than actual values. 

 For wave periods greater than 15 sec, this error was appreciably more, al- 

 though waves of this type occurred less than 1 percent of the time at the 



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