Capacitive sensing apparatus and methods

A method of capacitive sensing comprising:

• providing a capacitive senor comprising
• a first electrode;
• a displacement element moveably mounted relative to the first electrode;
• and
• a second electrode coupled to the displacement element so that displacement of the displacement element along a displacement direction changes a separation between the first electrode and the second electrode;
• and
• selectively operating in one of a displacement sensing mode and a proximity sensing mode, wherein
• in the proximity sensing mode, the second electrode is electrically coupled to capacitance measurement circuitry to measure a capacitance characteristic associated with the second electrode to detect the presence of an object in proximity to the second electrode;
• and in the displacement sensing mode, the second electrode is electrically coupled to a reference potential signal, and wherein when in the proximity sensing mode, the first electrode is electrically coupled to a time varying drive signal corresponding to a time varying drive signal applied to the second electrode by the capacitance measurement circuitry.

A capacitive sensor comprising:

• a first electrode;
• a displacement element moveably mounted relative to the first electrode;
• and a second electrode coupled to the displacement element so that displacement of the displacement element along a displacement direction changes a separation between the first electrode and the second electrode;
• and
• a controller element configured to selectively operate in a displacement sensing mode and in a proximity sensing mode, wherein
• in the proximity sensing mode, the controller element is configured to electrically couple the second electrode to capacitance measurement circuitry to measure a capacitance characteristic associated with the second electrode to detect the presence of an object in proximity to the second electrode;
• and
• in the displacement sensing mode, the controller element is configured to electrically couple the second electrode to a reference potential signal, and
• wherein the second electrode comprises a deformable electrode arranged between the displacement element and the first electrode, wherein the deformable electrode has a contact surface facing the first electrode and insulated therefrom by an insulator layer, and wherein at least part of the contact surface is inclined relative to an opposing surface of the first electrode such that when the deformable electrode is compressed along the displacement direction by a displacement of the displacement element relative to the first electrode there is a reduction in separation between the contact surface and the opposing surface of the first electrode.