Fig. 2. Tower array mounted on USS SEA DEVIL. 



5 knots and guy wire vibration is excessive at 



6 knots. There are 3^ thermistor beads in the 

 vertical array. Of these, 26 are spaced at 

 1-foot intervals and used with a digital data 

 system. Five are used as in the original array 

 except that they are spaced at 6-foot intervals . 

 The remaining 3 beads all have fast thermal 

 response and are used for continuous temperature 

 measurements. Two of these beads are located 

 near the middle of the tower while che third is 

 located at the top. In addition there is a fixed 

 resistor which is mounted at the foot of the 

 tower. 



It is clear that the motion of the platform 

 through the water causes an essentially time- 

 independent distortion of the streamlines about 

 the bow. This leads to a distortion of the time- 

 dependent vertical temperature structure and the 

 shape of the internal wave is modified. Since 

 the distortion is most severe near the hull, the 

 lowest beads are mounted some distance above it 



and data from the upper part of the strut are 

 preferred. 



TEMPERATURE INDICATING SYSTEM 



Thermistors were chosen as temperature sensor 

 elements because of their high sensitivity and 

 simplicity. Thermistors have a large negative 

 temperature coefficient of resistance and the 

 resistance is an exponential function of tempera- 

 ture. Commercially available thermistors do not 

 have the same resistance vs. temperature charac- 

 teristics (typical variations are ±20$ in nominal 

 resistance at 25°C) and hence are not directly 

 interchangeable. Since the feature of inter- 

 changeability in sensor units is very desirable, 

 a method was worked out for determining the 

 optimum values of 2 resistors, one in series and 

 one in parallel with the thermistor, that would 

 successfully match the sensor outputs. The ther- 

 mistors used were Veco 32A1 ("Victory Engineering 



50 



