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BELL SYSTEM TECHNICAL JOURNAL 



across these points of the order of 25 to 50 mmf, this source of error 

 may be neglected in the measurement of inductance. 



Table I gives the exact values for Cz and ri, and the corresponding 

 constant K by which the indicated value of R must be multipled to 

 give the true inductance. This table shows how accurately the 

 resistance Tx has been adjusted to make the bridge direct reading, 

 i^ is a simple number within .02 per cent in all cases when using the 

 large condenser. The two condensers might have been made to have 

 a ratio more nearly 10 to 1 by adding an auxiliary condenser to the 

 larger one. 



TABLE I 



K = Cz X Ti = Millihenrys per Ohm 



A check was next made on a single inductance having a nominal 

 value of .1 henry to determine the relative accuracy of different 

 values of K at different frequencies. These values are given in Table 

 II. It will be noticed that the value of L obtained is approximately 



TABLE II 

 CoMP.\RisoN OF Different Values of K Using a Single Inductance 



independent of K but the highest value obtained is for the value of 

 K corresponding to the highest value of ri. Since the reactance of 

 this coil is only approximately 600 ohms at 1,000 cycles and the 

 largest value of Vi used was 828 ohms, it is evident that the potential 

 of the coil with respect to ground varies considerably for different 

 values of K. This is sufficient to account for the increased inductance 

 value obtained for values of K using ri = 828 ohms. Keeping this 



