334 



WAVE ANALYSIS. 



[Ex?. 



4. We are given the ordinates of a complex wave. The 

 process of analysis consists first in determining the values of 

 A lf A 3 ,A 5 , etc., and B^B^B^ etc. These values may then be 

 substituted in (i) ; or, as is more useful, the values of C lt C 3 , C 5 , 

 etc., </>!, < 3 , </> 5 , etc., and a 3 ,a 5 , etc., are computed and substituted 

 in (2), (3) or (4). 



5. When the wave to be analyzed is given in the form of a 

 curve as an oscillograph record, for example the values of the 

 ordinates necessary for computation are measured from the 

 curve. In some cases, however, the values of the ordinates are 

 determined directly by experiment as in the determination of an 

 alternating current wave by the point-by-point method of instan- 

 taneous contact and in this case plotting the curve is unnecessary. 



The ordinates used must be equi-distant and must be known 



FIG. 2. Showing 18 ordinates taken in a half wave. 



for one half of a wave. The following method is based upon 18 

 ordinates for one half wave and is sufficient for determining the 

 amplitude and the phase of the odd harmonics up to and includ- 

 ing the seventeenth; even harmonics are assumed to be absent. 



