A capacitive sensor for detecting the movement of an object, particularly for detecting the actuation of a key of an operating unit, comprising - a first electrode (30;32), - a second electrode (34;36) provided for connection or mechanical coupling to, or for arrangement on, the object, the distance of the second electrode from the first electrode (30;32) changing when the object moves, - wherein the two electrodes (30,34;32,36) form a first capacitor (26;28) with a volume between the electrodes (30,34;32,36), the size of which changes when the object moves, and - an evaluation unit connected to the two electrodes (30,34; 32,36) and operative to determine a change of capacitance between the two electrodes (30,34;32,36) resulting from a change of their spacing and volume, - wherein a deformable, non-gaseous first dielectric is arranged between the two electrodes (30,34;32,36), - wherein the first dielectric defines at least one gas volume or, together with at least one of the two electrodes (30,34;32,36) defines a gas volume that is filled by a gaseous second dielectric, - wherein, when the two electrodes (30,34;32,36) approach one another, at least a part of the second dielectric escapes from the gas volume and from the volume between the two electrodes and, - wherein, when the two electrodes (30,34;32,36) approach one another, the portion of the volume between the two electrodes (30,34; 32,36) occupied by the first dielectric increases and the portion of the volume between the two electrodes (30,34;32, 36) occupied by the second dielectric decreases, characterized in - that the first dielectric is a shaped body formed in the manner of a lens and having two protruding outer sides facing toward the electrodes (30,34;32,36) and - that said gas volume is formed between the outer sides and the electrodes (30,34;32,36). - a first electrode (30;32), - a second electrode (34;36) provided for connection or mechanical coupling to, or for arrangement on, the object, the distance of the second electrode from the first electrode (30;32) changing when the object moves, - wherein the two electrodes (30,34;32,36) form a first capacitor (26;28) with a volume between the electrodes (30,34;32,36), the size of which changes when the object moves, and - an evaluation unit connected to the two electrodes (30,34; 32,36) and operative to determine a change of capacitance between the two electrodes (30,34;32,36) resulting from a change of their spacing and volume, - wherein a deformable, non-gaseous first dielectric is arranged between the two electrodes (30,34;32,36), - wherein the first dielectric defines at least one gas volume or, together with at least one of the two electrodes (30,34;32,36) defines a gas volume that is filled by a gaseous second dielectric, - wherein, when the two electrodes (30,34;32,36) approach one another, at least a part of the second dielectric escapes from the gas volume and from the volume between the two electrodes and, - wherein, when the two electrodes (30,34;32,36) approach one another, the portion of the volume between the two electrodes (30,34; 32,36) occupied by the first dielectric increases and the portion of the volume between the two electrodes (30,34;32, 36) occupied by the second dielectric decreases, - that the first dielectric is a shaped body formed in the manner of a lens and having two protruding outer sides facing toward the electrodes (30,34;32,36) and - that said gas volume is formed between the outer sides and the electrodes (30,34;32,36).