1002 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1952 



for their best performance, even though both bridges are useable at 

 higher fi'equencies. It will be observed that while there is some over- 

 lapping of the three ranges, all three methods are necessary to obtain 

 the impedance coverage shown. It should be emphasized that all the 

 ranges shown cover both capacitive and inductive reactances. In the 

 case of the admittance and series-reactance bridges, inductive imped- 

 ances are measured by using a resonating capacitor, in parallel or 

 series, respectively, with the apparatus being measured. In the Maxwell 

 inductance bridge, capacitive impedances are measured by using a 

 fixed resonating inductor in series with the impedance under test. A 

 complete accuracy statement for these bridges is necessarily complex, 

 but in general accuracies of ±0.25 per cent for the major component 



Fig. 2 — One-megacycle Maxwell inductance bridge, shown schematically in 

 Fig. Ic, designed for relay-rack mounting. 



