The present invention relates to a sensor device for determining an absolute angle of a prosthetic joint, and which is resistant to environmental elements and has a reduced power draw. The sensor device includes an inductive sensor and a rotatable member including a metal material. The metal material can include a non-ferrous metal material. The inductive sensor detects an amount of the metal material in a proximate location to the inductive sensor. Rotation of the rotatable member increases or decreases an amount of metal material in the proximate location of the inductive sensor. The amount of metal material in the proximate location corresponds to an angle of the rotatable member and the prosthetic joint based on a monotonic function. Thus, the inductive sensor detects the amount of metal material in the proximate location to determine the angle of the rotatable member and subsequently the angle of the prosthetic device.