Sec. 1-2] 



MECHANIC A L IX ITT TRA AN DCC K US 



27 



ways. The resistance wire can be wound on a card of varying cross 

 sections, as shown in Fig. (1-2)7. The shape of the card should follow 

 the derivative of the desired function. For instance, the resistance 

 between the terminals B and C in Fig. (1-2)7 increases with the square 

 of the contact displacement d. Another means to vary the output 



■*A 



^C 



-AAA/VVVV\A\aaa/YWvVt — °B 



Fig. (1-2)7. (a) Nonlinear poten- 

 tiometer; (6) relation between 

 output (resistance BC) and dis- 

 placement d of the moving con- 

 tact. 



/?, R 2 R-$ Ra, 



Fig. (1-2)8. Nonlinear potentiom- 

 eter adjusted by parallel resis- 

 tors i? x to R 4 . 



Fig. (1-2)9. Sine or cosine potentiometer. 



in the form of a nonlinear function consists in an approximation of 

 the desired function from linear segments between taps of the poten- 

 tiometer, as shown in Fig. (1-2)8. 



A potentiometer that furnishes an output proportional to the sine 

 or cosine of the shaft rotation is shown in Fig. (1-2)9. The potentiom- 

 eter consists of a rectangular card C, on which the resistance wire 



