POWER MEASUREMENT 



327 



the potential difference between the outer terminals of the con- 

 densers C. 

 Let the displacement along y be 



y = Kv 

 and that along x be 



x = K'vi. 

 K and K' are constants. 



Then for an elementary area, dA = ydx = KK'vdvi. 



I 



FIG. 192. Connections for Ryan power diagram indicator with condenser 



multiplier. 



The current i through the condensers is that taken by the 

 specimen, and 



Then 



C ' dvi 

 2 di 



2KK' 

 dA = 7: mdi 



and the area of the diagram is 



A = K" ( T mdt = k'P. 



The constant k' is determined by calibration. 



(25) 



