Bridged-T and Parallel-T Null Circuits for Measurements at Radio Frequencies

Bridged-T and parallel-T null circuits may, under some circumstances, be preferable to bridge circuits for radio-frequency measurements as no transformer is required and the generator and detector can have a common grounded terminal. An analysis of the circuits can be made in terms of the transfer impedances of the various possible component T networks so that the nature of possible null conditions becomes evident by inspection. The circuits considered include arrangements suitable for the measurement of resistance, reactance, and frequency, and of the power factor of dielectrics. Some of the circuits, particularly suited to high-frequency work, employ neither coils nor variable resistors.