It is clear that the response time is proportional to the 

 fluid viscosity and inversely proportional to the fourth power of the 

 tubing diameter. Changing the tubing length was not considered since 

 the lengths were pre-determined by the DPG configuration as descirbed 

 in Chapter II. 



It was first thought that the response time could be 

 sufficiently decreased by reducing the fluid viscosity. A number of 

 fluids were considered but all discarded because of their degrading 

 effects on the system's materials, (i.e., acrylic, neoprene, Buna-n, 

 nylon, and stainless steel). After two hundered and eighty hours of 

 nearly continuous laboratory work, it was decided to use gin as the 

 back-filling fluid. It is inexpensive, easily obtainable, safe, and 

 has a dynamic viscosity coefficient one and one half orders of 

 magnitude less than transmission fluid. The transducers and sensors 

 were drained of transmission fluid and flushed briefly with hexane, 

 then methanol, then back-filled with gin. A 50-50 combination of 40 

 proof McCalls and 80 proof Gilbeys gin was used. The water content 

 of the gin required that the fluid rest in the system for twenty-four 

 hours during rising temperatures so that air released from the water 

 could be collected and removed. 



Although the system response time improved, it remained 

 unacceptably high. It is crucial for each of the five DPG 

 transducers to respond quickly and simultaneously to ensure proper 

 instantaneous measurement of the sub-surface dynamic pressure. 



