-EXTRUDED POLYETHYLENE COVER 



-3/S2"dIA 7X7 PLOW STEEL WIRE ROPE 



NICHROME RESISTANCE WIRE 



WX 7 WIRE ROPE 



Fig. 1. Construction of active element. 



-NICHROME SOLDERED 

 TO WIRE ROPE 



•THIMBLE 



SOLDER JOINT RECOVERED 

 WITH POLYETHYLENE 



CABLE CLAMP 



Fig. 2. Electrical and physical terminations. 



Finally, the ambient temperature range over 

 which the system will operate within its rated 

 accuracy specifications is an important considera- 

 tion. Once the output level is set, the system 

 should retain its accuracy over a range of ±25°F. 

 The system should operate over a range of 0° to 

 1*4-0 F with a slight degradation of accuracy. 



TRANSDUCER 



The basic transducer, more commonly referred 

 to as the staff, evolved in the process of 

 achieving the previously described specifications . 

 Several different configurations can be used for 

 the active element that fundamentally consists of 

 a continuous resistance wire. The particular 

 staff described below is a polyethylene jacketed 

 wire rope of suitable physical strength wound in 

 a continuous spiral with a Nichrome resistance 

 wire. The resistance wire is lightly embedded in 

 the polyethylene giving a near smooth surface 

 offering minimum interference with water runoff 

 (Fig. l). The out-of-the-water resistance for 

 all staff lengths is 2,000 ohms. To accomplish 

 this for staffs of different lengths, either the 

 wire size or winding pitch of the wire on the 

 staff is varied, or both. 



The strength of the polyethylene jacketed wire 

 rope can be selected for compatibility with in 

 situ operational requirements. Cable sizes 

 allowing tensions on the order of 2,000 pounds 

 have been utilized; however, the fouling rate 

 from marine organisms appears to increase in 

 excessive proportion to the increase in wetted 

 surface area of the staff. Polyethylene has been 

 demonstrated to have excellent resistance to 

 deterioration in sea water and fortuitously has 

 the characteristic of "memory, " which facilitates 

 the assurance of a tightly wound resistance ele- 

 ment. In addition, polyethylene is quite readily 

 replaced in areas where exposure of the wire rope 

 is required in the construction of the active 

 element (Fig. 2) . A small soldering iron fitted 

 with a spatula shaped tip, solid polyethylene 

 spaghetti as the "soldering" material, plus a 

 simple technique similar to conventional soldering, 

 is all that is required to accomplish completely 

 homogeneous and leakproof restoration of the 

 polyethylene jacket. The lower end of the staff 



s* 



