A method of sensing an amplitude and a phase of a varying electrical signal representing an impedance of an electrically conductive tissue through which an AC stimulation current is forced may include measuring a first amplitude value of the varying electrical signal corresponding to an arbitrary initial phase offset value and assuming the first amplitude value corresponds to the amplitude and assuming the arbitrary initial phase offset value corresponds to the phase. The method may include measuring a second amplitude value of the varying electrical signal at a phase offset different from the phase. The method may further include comparing the second amplitude value with the amplitude, and updating the amplitude and the phase to correspond to one of a maximum and a minimum amplitude value and to a corresponding phase offset.
