MEASUREMENT OF PHASE DISTORTION 



533 



so that all points in this side of the network are at the same potential, 

 the measurements may be made with the arrangements shown on the 

 right of the figure. In the latter case, the measured impedance is four 

 times that obtained for an equivalent system by the method shown on 

 the left of the figure; and in plotting these values for comparison with 

 those obtained by the method of Fig. 4, one fourth of the measured 

 values should be used. The results obtained in this way are evident 

 from what has already been described and will not be illustrated here. 



BALANCED SYSTEM 



UNBALANCED SYSTEM 



SYSTEM 



TO BE 



MEASURED 





SYSTEM 



TO BE 



MEASURED 



U 

 iij9 



2ID 



K J K 



UJ 



o 



LJ Q 

 1 (O 



K= CHARACTERISTIC IMPEDANCE OF SYSTEM 



Fig. 6- — Modified arrangement for special impedance measurements. 



(Short termination.) 



As before, the curve passing through the points of intersection of the 

 impedance curves corresponding to the open and short terminations 

 should be used as the axis in determining the length of impedance 

 cycles. For the network illustrated in Fig. 5, the resistance curves 

 would intersect on the line +150 ohms, while the corresponding re- 

 actance curves would intersect on the zero line. The delay obtained in 

 this way is the delay of the system between characteristic impedances. 

 When other impedances are bridged across the measuring trunk than 

 those shown in the figures, the delay measured is the insertion delay 

 between impedances having the same relation to the actual bridging 

 impedance as K has to the value of bridging impedance shown in the 

 figures. 



In most practical cases, the characteristic impedance of the network 

 to be measured is a pure resistance and the network is designed to work 

 between this impedance at each end. The value of resistance which 



