A sensor for sensing proximity or touch of an object includes a sensing region, an oscillating signal generator for generating an oscillating signal having an oscillation period, a gating signal generator for generating a gating signal having a gating duration, a controller for controlling the oscillation period or the gating duration and a processor for determining a number N of oscillation periods over the gating duration. The number N is indicative of the object's contact with, or proximity to, the sensing region. The sensor is calibrated by determining an optimal value for the oscillation period or gating duration such that an optimal number N over the gating duration is expected.