- 105 - 



mean of the center and arm sensor vertical positions above the 

 bottom. The gage length dx was 3.5 feet. For configuration I, the 

 estimated angle, 51.3°, compares well with the 55° angle expected. 

 For configuration II, the estimated angle is 35.4° compared to an 

 expected value of 35°. 



The experiment at CERC, although plagued with arm sensor 

 failures and highly non-linear waves, demonstrated the capability of 

 the instrument to measure wave direction. The tests also served the 

 purpose of defining several important modifications required to 

 improve the performance of the DPG system. 



E. The Second DPG Prototype 



The DPG was returned to the University of Delaware laboratory 

 and partially disassembled to install the new hardware modifications. 

 The fracture of the arm lines of dPl, dP2, and dPA were confirmed. 

 All of the stainless steel tubing exterior to the water-tight 

 instrument cylinder was replaced with flexible tubing and 

 back-filled, and the system was calibrated as described in Section C 

 of this chapter. New PVC arms were machined to house the flexible 

 tubing and isolation diaphragms and the instrument was reassembled as 

 described in Appendix D. Care was taken to ensure that the sensors' 

 elastomer diaphragms were well back from the ends of the PVC arms and 

 exposed to the holes in the sides of each arm. Some dimensions of 



