Abstract :
The paper describes a high-accuracy measuring circuit suitable for frequencies from 50c/s to v.h.f. There are two branches in the circuit, one of which contains the unknown impedance. The two branches are fed in phase opposition from the secondaries of two mutual inductors or two transformers. Due to the feeding in opposition of the two branches, the transfer impedances are very simple, no negative real terms are present and no more than two variable standards are required for balance. The balance equations in the majority of cases do not contain the term ¿ (angular frequency), the frequency need not therefore be known very accurately and the calculations are simple. Furthermore, at balance, the detector, source and all the circuit components except one have one terminal connected to earth. The potentials are therefore fixed and most of the capacitances to earth are eliminated; those that remain shunt one secondary and the standard in one branch of the circuit and can easily be determined or otherwise taken into account in the calculations. Tests have been made over a wide range of resistance, inductance and capacitance between 100c/s and 50Mc/s. The error varied, according to the standards and the frequency used between ±0.001% and ±0.01%.
