A multi-frequency inductive sensing system can be used for spectrographic material analysis of a conductive target material (such as tissue) based on electrical impedance spectroscopy. An inductive sensor can be driven with an excitation current at multiple sensor excitation frequencies (ω) to project a time-varying magnetic field into a sensing area on the surface of the target material, inducing eddy currents within the target material. The inductive sensor can be characterized by a sensor impedance Z(ω) as a function of the sensor excitation frequency (ω), and the resulting induced eddy currents. Multiple sensor impedance Zs(ω) measurements, at the multiple sensor excitation frequencies (ω), can be determined, which represent electromagnetic properties of the target material (such as permittivity ε, permeability μ, and resistivity ρ), based on the induced eddy currents. The multiple sensor excitation frequencies (ω), and corresponding multiple sensor impedance Zs(ω) measurements, can be selected for particular target penetration depths.
