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BELL SYSTEM TECHNICAL JOURNAL 



made by comparison with capacitance and resistance or with capaci- 

 tance and frequency. The resonant method is adapted to the com- 

 parison of inductance with capacitance and frequency. However, 

 this method demands an accurate measurement of the frequency used, 

 which is not always convenient. It is therefore evident that a bridge 

 which furnishes a comparison of inductance with capacitance and 

 resistance serves a very useful purpose in the calibration of standards 

 of inductance for use in simple comparison bridges. 



A bridge circuit due to Owen ^ furnishes a very good example of 

 this type, the balance conditions being independent of frequency and 

 the equations of balance giving a relation between inductance, capaci- 

 tance, and resistance. The circuit is shown in Fig. 1. It consists of 

 a fixed resistance ri in the arm BC, a fixed capacitance C3 in the arm 

 AB, a fixed capacitance d in series with a variable resistance R in 



RECEIVER 



Fig. 1 



AD, and a variable resistance ro in series with the inductance to be 



measured in CD. The adjustments for balance are made with R 



and ^2. These two adjustments are independent of each other. The 



relations between the quantities at balance, as will be shown later, 



are such that the bridge may readily be made direct reading for 



' D. Owen, "A Bridge for the Measurement of Self Induction," Proceedings of 

 Physical Society of London, Oct. 1, 1914. 



