DIRECT-COUPLED PRE-AMPLIFIERS 



Set 

 circulating 

 current to 

 1mA 



•750il 



Unit dry A± 

 cell -r_ 



Push button c^ 



100 il 

 100 i^ 

 100 fi, 

 100 ii 

 100 il 

 100^ 



100 a 

 100 ft 

 100 fl 



Hundreds 



of millivolts 



selector 



switch 



Figure 39.15 



Tens of 

 millivolts 



selector 



switch 



+ 

 -o 



Calibrator 

 output 



10.186 Q 



25-0-25 

 llA meter 



Checkir Weston 



button standard 



cell 



/ 



_:^ iVzv 



'- Leclanche 

 cell 



3-3 k 



100^2 



Polarity 

 reversing 

 switch 



S 



^ 



100 u 

 p,A 



— WVy^/ 



Set 



circulating 



current 



lOQ 



42 



Figure 39.16 

 629 



Tens of millivolts 

 selector 



switch 



Output 



Millivolts 

 selector 



switch 



