CO 

 UJ 



tr 



UJ 



Q- 



< 

 O 

 tr 

 o 



a. 

 a: 



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 o 



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5 OHMS 



1 6 OHMS 



TERMINAL VOLTAGE MILLIVOLTS 



Fig. k. Characteristics of cells at low illuminations (active area, 11 cm 2 ). 



potentiometer or a high input resistance milli- 

 voltmeter. On such a plot the external resis- 

 tances are seen as diagonals. The end points of 

 the curves on the current axis are the short cir- 

 cuit currents and the end points on the potential 

 axis are the open circuit voltages . The curves 

 give the mean values for 3 cells of each type. 

 It is seen that the new type cells are appre- 

 ciably more sensitive than the old type. 



The improvement is seen to "be much more pro- 

 nounced at light levels below 1 foot candle. The 

 light levels, shown in Fig. k, range between 0.1 

 and 1 foot candle and the external resistances 

 from 100 ohms to 1 megohm. While the short cir- 

 cuit currents of the new type cell are appre- 

 ciably larger, the open circuit potentials 

 exceed those of the old type by more than an 

 order of magnitude. The difference is more pro- 

 nounced the lower the light level. A pronounced 

 increase in performance is present also in the 

 maximum power capabilities of the cell. The maxi- 

 mum power is obtained from the limiting power 

 diagonal at a given light level. 



The output current is seen replotted as a 

 function of the illumination of Fig. 5- With low 

 values of external resistance the output is 

 linear with respect to the light level. The open 

 circuit potential, on the other hand, increases 

 rapidly at first and gradually later and satu- 

 rates at higher light levels, as seen in Fig. 6. 



100 



1000 EX1 RES 



200° OHMS 



ILLUMINATION -FOOT CANDLES TUNGSTEN LIGHT 2700° K 

 ■ '_l I II I I 11 



Fig. 5- Current output of new cell as a function 

 of illumination (active area, 11 cm2) . 



185 



