16 



first selecting an instrument deployment depth according to the site 

 and the wave frequencies that are of most interest or are ir.ost likely 

 to be encountered — remembering that deeper installations require 

 more sensitive transducers. A maximum wave height at the most 

 sensitive frequency for the chosen depth is then considered with the 

 manageable gage length restriction in mind. The maximum differential 

 pressure is then calculated from Equation 2.2. The result is an 

 estimate of the rated capacity of the transducer needed. This 

 estimate is then used to select a transducer available from industry. 

 One next considers the noise level of the system to determine whether 

 the selected instrument is capable of reporting the minimum 

 differential pressure of interest, (i.e., a small amplitude wave of 

 frequency higher or lower than that of the instrument's most 

 sensitive range at the chosen depth). Satisfied with the results, 

 the gage length, ax, is fine-tuned based on the rated capacity of the 

 transducer, R, and the maximum wave of interest. From Equation 2.2, 



Ax = ; ^^^ C2 A") 



Y H k cos K y^-^) 



P 



The instrument's response to a minimum wave condition is checked 

 again using the newly calculated gage length to ensure that a 

 reasonable signal to noise ratio is maintained for small amplitude, 

 long period waves. 



