The disclosure comprises: linking a first terminal of the capacitance to the mid-point of a first voltage divider bridge, applying a first voltage to a second terminal of the capacitance, maintaining a voltage of a mid-point of the first divider bridge near a reference voltage, and discharging a mid-point of a second divider bridge with a constant current. When a voltage of the mid-point of the second bridge reaches a first voltage threshold, applying a second voltage to the second terminal of the capacitance, and measuring the time for the voltage to reach a second threshold.