151 



For DPG operation in water depths of 20 feet, the absolute 

 pressure transducer should be changed from 50 psia rated capacity to 

 30 or 35 psia to improve resolution. 



Different designs of the isolation sensor diaphragms could be 

 considered in order to create a sensor that is easier to back-fill 

 and less difficult to machine. When calibrating the sensors, an 

 oscillating pressure pump used in conjunction with the calibration 

 system described in Section V.C.I might better estimate the system's 

 dynamic loading characteristics. Temperature effects upon the 

 transducers and their respective sensors should be investigated more 

 thoroughly during instrument calibration. 



The effects of vortex shedding about the sensor diaphragms 

 might be investigated. The sensors could be re-configured within the 

 PVC arms and fuselage to minimize vortex shedding effects if they are 

 found to be of sufficient magnitude for some application of the DPG. 

 Tests in the large wave tank at the Coastal Engineering Research 

 Center suggest that the configuration of the sensors within the arms 

 is important for accurate directional estimates, (Section V.D.3). 



Although a tripod was at one time considered for the 

 instrument cradle, the four-legged cradle used for the DPG at the 

 Field Research Facility proved stable and easy to maneuver in the 

 installation and first weeks of operation in the field. Future DPG 

 systems may retain this four-legged cradle or experiment with a 



