Parallel-Resonance Methods for Precise Measurements of High Impedances at Radio Frequencies and a Comparison with the Ordinary Series-Resonance Methods

Two parallel-resonance methods are described which determine primarily the parallel conductance of a parallel-tuned circuit. They are most useful for measuring relatively low admittances (high impedances). Since they are duals of the reactance- and resistance-variation methods, they have been named the susceptance- and conductance-variation methods. These parallel-resonance methods are compared with the series-resonance methods with respect to range and possible sources of error. It is pointed out that, for substitution measurements, tight coupling to a constant-frequency power source need not introduce errors in measurements with either series- or parallel-resonance methods. The errors caused by residual inductance and metallic and dielectric loss in the standard condenser are discussed and numerical examples given. A precise method of interpreting resonance-curve data is presented. Experimental results are listed for measurements of high resistances by the susceptance-variation method.