A sensor assembly (26, 30) for measuring relative rotary movement about a pivot joint having an axis of rotation (28, 32) between a first member and a second member (20, 12) comprising: - a housing having a proximal end and a distal end and an inner surface, the proximal end fixedly secured to the first member; - a first fitting having an outer surface and an opening, the outer surface abutting the inner surface of the housing between the proximal end and the distal end, the opening formed in the first fitting being substantially parallel to the axis (28, 32) of the pivot joint; - a sensor secured to the opening and facing the proximal end of the housing; - a shaft rotatable about the axis (28, 32) of the pivot joint and affixed to the sensor and extending through the opening of the first fitting, the shaft journaled along a portion of the opening of the first fitting that faces a distal end of the housing; and characterized in that the assembly further comprises: - a flexible coupling configured to fixedly receive a portion of the shaft extending from the opening of the first fitting so that the flexible coupling and the shaft rotate together; - a first pair of pins extending from the flexible coupling; - a cap rotatable about the axis (28, 32) of the pivot joint and having an outside surface, a first pair of openings, and a second pair of openings, the outside surface of the cap corresponding to the inner surface of the housing, the first pair of openings configured to receive the first pair of pins extending from the flexible coupling, the second pair of openings configured to receive a second pair of pins extending through the distal end of the housing; - a bracket (65, 130) secured to the second member (20, 12) and extending to a slot (66, 131) configured to receive the second pair of pins. - a housing having a proximal end and a distal end and an inner surface, the proximal end fixedly secured to the first member; - a first fitting having an outer surface and an opening, the outer surface abutting the inner surface of the housing between the proximal end and the distal end, the opening formed in the first fitting being substantially parallel to the axis (28, 32) of the pivot joint; - a sensor secured to the opening and facing the proximal end of the housing; - a shaft rotatable about the axis (28, 32) of the pivot joint and affixed to the sensor and extending through the opening of the first fitting, the shaft journaled along a portion of the opening of the first fitting that faces a distal end of the housing; and - a flexible coupling configured to fixedly receive a portion of the shaft extending from the opening of the first fitting so that the flexible coupling and the shaft rotate together; - a first pair of pins extending from the flexible coupling; - a cap rotatable about the axis (28, 32) of the pivot joint and having an outside surface, a first pair of openings, and a second pair of openings, the outside surface of the cap corresponding to the inner surface of the housing, the first pair of openings configured to receive the first pair of pins extending from the flexible coupling, the second pair of openings configured to receive a second pair of pins extending through the distal end of the housing; - a bracket (65, 130) secured to the second member (20, 12) and extending to a slot (66, 131) configured to receive the second pair of pins.