MEASUREMENT OF INDUCTANCE 



381 



they simply shunt the input and output circuits, and to AB where 

 they shunt the capacitance Cz and may be included in the assumed 

 value of C3. If such shielding is not used, the balance of the bridge 

 will be affected by external conditions such as body capacitance, and 

 the position of the bridge arms with respect to each other and to other 

 apparatus, with the result that accurate results can be obtained 

 only by the use of the greatest precautions. 



A shielding scheme which satisfies the above requirements is shown 

 in Fig. 2. In this system all capacitance between shields is limited 

 to the diagonal corners of the bridge and the arm AB. However, 

 this system of shielding, while about as simple as can be designed 

 where complete shielding is required, is rather difficult to carry out 

 in any practical bridge construction. 



9^JLftMMftMA>-9 



II II 

 GENERATOR 



Fig. 3 



The question of reducing the amount of shielding and still retaining 

 a high degree of accuracy has been investigated and the modified 

 scheme shown in Fig. 3 has been developed. In this circuit the 



