W. Masoyi — Nen Ilarmonic Analyser. 



489 



cially noticed that the axis of the wave form must be 

 traced as well as the wave form itself, for otherwise no 

 closed area would be obtained. The derived area will 

 consist of a number of loops, the number depending on 

 the harmonic analyzed for, and the size and shape of the 

 wave form. Fig. 3 shows a sample wave form and 

 derived area for the first sin harmonic. Every time the 

 lines cross over the sign of the area changes. On all 



Fig. 4. 



Humbe.rs> on curve. 3 indicate, order o-/^ harmonjc 



polar or rolling planimeter positive area is that area 

 which is measured in a clockwise direction, while if the 

 direction" of rotation is reversed, the value recorded has 

 a negative sign. This fact can be utilized in the summing 

 up of the positive and negative areas at one reading, for 

 if the tracing point of the planimeter follows the tracing 

 point of the analyzer in the exact path traced by it, the 

 tracing point of the planimeter will go around the positive 

 loops in one direction and the negative loops in another. 



