Battery-less Active Float for Inductive Sensor for Monitoring Fluid Level and Displacement

A fluid level sensor system includes a primary coil, at least one secondary coil adjacent the primary coil, a control system operative for applying a time varying signal to the primary coil and for detecting a response of the secondary coil to the time varying signal in the primary coil, and at least one float resonator adapted to move adjacent the primary and secondary coils. Each float resonator includes an electrical storage device and a circuit which is switchable between a first state that enhances the response of a section of the secondary coil adjacent the float resonator to the time varying signal in the primary coil and the charging of the electrical storage device, and a second state where the effect of the circuit on the response of the secondary coil to the time varying signal in the primary coil is diminished relative to the first state.