The chain hoist is a self-powered winch designed for work re- 

 quiring measurements to 250 meters depth at slow ship speeds, and to about 

 160 meters depth at a speed of 13 knots. 



The 34 thermal sensing heads are type GB 32 P168 thermistors 

 placed at intervals of 9 meters. The beads are matched to one part in two 

 thousand which is 0.02° at the matching temperature. The chain is designed 

 so that a defective thermistor can easily be changed by unplugging a 

 small unit and inserting a new one. 



The contouring temperature recorder plots the vertical distri- 

 bution of temperature as a continuous record. Each isotherm is displayed 

 as a depth profile similar to that given by an echo sounder. The recorder 

 uses a helical drum and blade principle and writes on electrosensitive 

 paper. 



The measuring circuits cover a range from -20 C C to 32°C and 

 10 isotherms can be plotted for this entire range. When gradients allow 

 finer plotting, 0.1° or 0.05° isotherms can be recorded. The rate of 

 scan can be varied, but 12 seconds is the optimum time for taking the 

 temperature information for the near vertical column of water, a surface 

 bead and the pressure sensor. The isotherms are obtained in 8 seconds; 

 the remaining 4 seconds are used for the depth and surface measurements. 



The depth sensor is a Bourdon tube driving a potentiometer. 

 The d-c output signal from this potentiometer is balanced against the 

 d-c feed back from the feed back potentiometer in the depth servo-mechanism. 

 The balanced signal is then amplified by a conventional 400 cycle servo- 

 amplifier. The depth is recorded on the lower portion of the paper record. 



19 



Arthur ZB.lLtttleJnr. 



