A method and a system are provided to determine fill sufficiency of an electrochemical biosensor test cell by determining capacitance of the electrochemical test cell. In particular, the system samples an output signal from the chamber at a second sampling-time interval different than a first sampling-time interval such that a magnitude of each sampled output signal is measured at each succession of the second sampling-time interval instead of at the first time interval. The system determines a phase angle between an output signal and the oscillating input signal from the chamber based on the sampled output signal of the sampling step. The system calculates a capacitance of the chamber from the phase angle. A method is also provided to perform similar functionalities of the system.