UNDERWATER TELEMETER FOR DEPTH AND TEMPERATURE 



A complete communication system consists of a transmitter, a 

 transmission medium, and a receiver. In a telemetering system, 

 the transmitter encodes or translates the desired infoimation into 

 a foim which may be easily carried by the transmission medium and 

 which may then be reclaimed at the receiving end. In many cases 

 where high accuracy or high fidelity is required, serious design 

 problems are encountered because each link of the telemetering 

 "chain" has the ability, in one way or another, to scramble the 

 information being transmitted and to destroy accuracy. Therefore, 

 it becomes the duty of the design engineer to evaluate the variables 

 and the sources of error and to use all the facilities at his command 

 to maintain coherence of the information being transmitted. 



Required performance 



It was necessary to design an instrument to give continuous 

 depth information over a range from to 200 fathoms with a resolution 

 accuracy having an error of not more than + 1 percent. Reliable trans- 

 mission was required over a distance of 5*000 feet. 



The specified performance requirements determined the basic 

 design of the instrument. In addition to accuracy, stability, oper- 

 ating distance, and operating time, there were numerous mechanical 

 aspects to be considered, such as pressure seals and housings. The 

 following sections present a detailed description of the completed 

 instrument. 



THE TELEMETERING SYSTEM 



The telemetering system chosen for the instrument described in 

 this report is a compromise. The problems of time, cost, and conven- 

 ience weighed heavily in the electronic and mechanical design, and 

 the finished unit is neither intended nor offered as the ultimate. 

 However, the instrument seems to work exceptionally well and may prove 

 to be a dependable and flexible device, which, through modifications 

 or variation, could provide numerous services to studies of oceanography 

 and marine biology. 



In order to obtain high resolution, an FM system was chosen in 

 which exceptionally large deviations are used to express the desired 

 variable depth. This is the major difference between the present 

 design and that developed by Willard Dow, which used straight primary 



