F G H 



Fig. 6. Contouring temperature recorder: 



(a) isotherms, (b) surface temperature 

 plots, (c) depth of end of chain plot, 



(d) patch panel for incoming leads, 



(e) recorder paper case, (f ) scan 

 temperature dial, (g) station tempera- 

 ture dial and (h) transducer depth dial. 



at those stations . A block diagram of the pro- 

 filer system is shown in Fig. "J. 



A commutating switch connects these stations 

 sequentially to the interpolating potentiometer 

 which assumes a linear temperature gradient 

 between any two successive stations. As the 

 wiper of this interpolating potentiometer travels 

 along its resistance path the wiper picks off a 

 uniformly graduated voltage between successive 

 thermistors. Since the water temperature at the 

 thermistors will not fall at whole degrees Centi- 

 grade (nor even at whole tenths of degrees), it 

 is necessary for the potentiometer to interpolate 



between degrees and fractions of degrees to obtain 

 whole degrees Centigrade or tenths of degrees. 

 The interpolated voltage produces a continuous 

 gradient that can be followed by an amplifier and 

 servo-mechanical components. This scan voltage 

 is fed into a scan servo-amplifier. 



The servo-amplifier and its associated follow- 

 up mechanism comprises a DC amplifier loop. The 

 feedback from the potentiometer on the servo- 

 mechanism is a nonlinear function adjustable to 

 the nonlinearity in the thermistor output voltage. 

 The nonlinearities cancel, producing an output 

 shaft rotation that is linear with reference to 

 temperature variations. 



Since the output of this servo-mechanism is 

 linear with temperature, it is only necessary to 

 provide a pick-off suitable for printing on a 

 record, such as slotted or digitizing drum driven 

 by a scan servomotor through gearing so arranged 

 that one turn of the motor equals 1°C. The drum 

 is slotted for l/lO° and l/20°C marks. These 

 slots allow light to actuate photoelectric cell 

 pick-offs whose outputs operate the print coder, 

 print amplifier and recorder at the moment of 

 passing through a given temperature. As the 

 linear interpolation progresses down the record 

 temperature marks appear at the same depth as 

 long as the temperature at the thermistor beads 

 remains constant. 



The measuring circuits cover a range from 

 -20°C to 32°C and 1° isotherms can be plotted for 

 this entire range. When gradients allow finer 

 plotting, 0.1° and 0.05° isotherms can also be 

 recorded. While the rate of scan can be varied, 

 12 seconds is the optimum setting for the overall 

 cyclic process of taking temperature information 

 from the nearly vertical column of water, the 

 surface bead and the pressure sensor. At this 

 setting the isotherms are contoured in 8 seconds, 

 the remaining k seconds being used for plotting 

 depth and surface. 



Depth Sensing Element 



The depth sensing element is a Bourdon tube 

 driving a potentiometer. The DC output signal 

 from this potentiometer is balanced against the 

 DC feedback from the feedback potentiometer in 

 the depth servo-mechanism. The balanced signal 

 is then amplified by a conventional ^00-cycle 

 servo-amplifier. 



The depth of the pressure transducer is 

 recorded on the lower portion of the paper record 

 which is interrupted every 6 minutes while the 

 scale marks are printed. This interruption dis- 

 tinguishes the depth record from the temperature 

 line. The vertical scale marks represent depth 

 at 60-foot intervals from the surface and they 

 are 6 minutes apart horizontally. 



57 



