US Patent 9158422 Capacitive rotary encoder

A human machine interface includes a capacitive touch screen having a capacitive sensor. The capacitive touch screen displays text characters and/or graphical information. A control device is rotatably coupled to a structure such that the control device is superimposed over the screen. The control device includes at least one electrically conductive element. The control device rotates about an axis substantially perpendicular to the screen such that the at least one electrically conductive element follows the rotation of the control device. The capacitive sensor senses a rotational position of the at least one electrically conductive element.