LOW FREQUENCY BRIDGE FOR GUARDED 3-TERMINAL AND 4-TERMINAL MEASUREMENTS OF ADMITTANCE

The null method described permits either guarded three-terminal or four-terminal potential probe measurements of conductance from 1 kHz to dc and of capacitance to frequencies as low as 0.01 Hz. Sample currents to a null detector are balanced by adjustable currents derived from dc voltage inverter and follower circuits which drive fixed standards of conductance and capacitance. Procedures for minimizing errors from circuit residuals and results of representative measurements are described. © 1969 The American Institute of Physics.