Sec. 1-2] 



MECHANICAL INPUT TRANSDUCERS 



49 



Displocement 



from a constant-current generator. Increase of the primary voltage 

 also leads to an increase of the distortion of the output waveform 

 (e.g., an increase of the applied voltage from 6 to 9 volts increases the 

 content of higher harmonics in the out- 

 put from 0.8 to 1.2 per cent; an increase 

 to 12 volts increases the distortion to 

 2.25 per cent). The sensitivity also 

 varies with the frequency of the applied 

 a-c voltage, as shown in Fig. (1-2)31. 

 The sensitivity varies but slowly with 

 frequency, so that precise frequency 

 control of the supply voltage is usually 

 not required. 



A residual voltage generally remains 

 when the core is at the zero position. 

 Fig. (1-2)30. This zero voltage, which is 

 normally less than 1 per cent of the 

 maximum output voltage in the linear 

 range, has its origin in an incomplete 

 magnetic or electric balance; it maj^ 

 consist of the fundamental frequency or 



Displocement 



Fig. (1-2)30. Linear variable 

 differential transformer, transfer 

 characteristic (Schaevitz Engi- 

 neering Corp., Camden, N.J.; by 

 permission). 



o 

 > 



0.01 



00 



o 



E 



10 



60 100 



1 

 10,000 20,000 



1,000 

 Frequency, cps 



Fig. (1-2)31. Linear variable differential transformer; 

 nominal full-range output and primary current versus 

 frequency for the type 100SS-L {Schaevitz Engineering 

 Corp., Camden, N.J.; by permission). 



