THEBUISTOB BE1D 



Fig. 1. USMEL sea temperature profiler (thermistor chain) hoist on USS MAEYSVILLE. 



harness. The plastic fairings that form the 

 trailing edge of each link serve to reduce drag 

 and hold the electrical conductors in position. 

 When the harness is inserted in the channel, the 

 plastic fairings are pushed into place between 

 the cheek plates and are held in position by 

 springs which snap into holes in the cheek plates . 

 To prevent tension in the harness when the chain 

 is bending sharply over the towing sheave, the 

 harness is looped into two rounded depressions in 

 the fairings. The 3^ fairings that hold tempera- 

 ture sensors have a drilled hole for insertion 

 of the thermistor bead and a drilled diagonal 

 channel that permits water to flow over the bead 

 as the chain is towed through the water. At the 

 lower end of the chain a streamlined, 2,300 pound 

 weight holds the chain in a nearly vertical posi- 

 tion while it is being towed. 



Fig. 2. Chain links, harness and fairings. 

 A B C D E f 



Fig. 3- Encapsulated thermistor bead: 



(a) thermistor bead, (b) phenolic 

 resin, (c) silicone rubber, (d) "0" 

 ring seal, (e) silicone rubber cap 

 and (f) leads. 



Beads and Connectors 



The thermal sensing beads used are type GB 32 

 Pl68 thermistors whose resistance varies as a 

 function of temperature, yielding ambient tempera- 

 ture measurements in the form of electrical cur- 

 rent amplitude. The beads are carefully matched 

 at a fixed temperature to an accuracy of 1 part 

 in 2,000, equivalent to 0.02°C, at the matching 

 temperature. Each bead and its two connecting 

 leads are encased in silicone rubber (Fig. 3)- 



5^ 



