priate to its sinking rate. If it operates on a digital principle or if 

 it has digital readout, its output must be quantized sufficiently finely 

 so as not to obscure any detail that occurred in the velocity profile, even 

 though this detail may be finer than the long term stability or accuracy 

 of the instrument. On the other hand, the comparatively modest absolute 

 accuracies required in this special application may permit the use 

 of principles probably not accurate enough for oceanographic work. Thus, 

 phase measurements on free propagating continuous waves, simple time/ 

 distance methods, or the counting of modes of high order in resonators 

 which operate at fixed frequencies could be employed. It is, however, dif- 

 ficult to think of anything more simple and efficient than the sing around 

 circuit . 



Taking advantage of these special conditions, it would be reason- 

 able to consider the design of an expendable instrument of bulk and cost 

 comparable to the expendable Bathythermograph. Two such designs, the "Ex- 

 pendable Sound Velocimeter" of Dyna Empire, Inc. , and the "Aquasonde" of 

 Tele-Dynamics Division of American Bosch Arma Corporation have already been 

 tested by the Naval Oceanographic Office (see Table III-2) . Other systems, 

 such as a freefalling expendable single wire system similar in appearance 

 to the XBT (Reference 31) have been proposed and undoubtedly others have 

 been thought of, designed, and tested. 



4. Possibilities of Hybrid Systems for Maximum Cost Effectiveness, and 

 Recommendat ions 



Not the least among the considerations that must be kept in mind 

 by instrumentation system designers is that users of successful systems 

 place great and unquestioning faith on the system and its performance. This 



46 



Arthur 2l.1Uttle.3nr. 



