Simultaneous determination of resistivity and susceptibility in an ac-susceptometer

We derive expressions for the in-phase and quadrature components of the output voltage of a balanced double transformer of cylindrical symmetry, typically employed in laboratory ac susceptometers. The expressions are developed for the case of cylindrical samples of finite length, excited by low-frequency fields. Investigation of the conductivity dependence of the output voltage, carried out with samples of commercial copper of different radii, validates the expressions.