A skin interface device (“SID”) for a cardiac assist device, including a SID cap having a first housing, an annular sleeve, and a first annular winding disposed over said annular sleeve. The SID further includes a SID base having a second housing formed to include a tubular portion, a cylindrical member disposed in said tubular portion, and a second annular winding disposed around said cylindrical member. The SID cap is configured to be rotationally attached to said SID base. When the SID cap is attached to the SID base, the second annular winding is disposed within the first annular winding, and the relative positions of the first annular winding and the second annular winding are fixed both laterally and vertically.