An inductive sensing system is adapted for noninvasive measurement of blood flow through a blood vessel. A resonant sensor is disposed in proximity to the blood vessel, and includes a coil resonator that generates a magnetic field within a sensing area that includes the blood vessel. The resonator changes resonance state based on changes in a flow of blood hemoglobin through the sensing area. The IDC unit establishes an IDC control loop, including the resonator as a loop filter, that provides feedback resonance control of the resonator to maintain a resonant frequency state (steady state oscillation) representative of blood hemoglobin flow through the sensing area. A feedback resonance control signal provides sensor data corresponding to the resonant frequency state as representative of blood flow through the sensing area. In one embodiment, the IDC control loop is implemented as a negative impedance control loop, controlling negative impedance to counterbalance resonant impedance.
