Abstract: A fringe field, capacitive distance sensor for measuring the distance between a probe and the surface of the conductive body. The sensor comprises a conductive plate element mounted by the probe, the thickness of the plate element being substantially less than the height and width of the plate element. The plate element is positioned adjacent to and normal to the body surface, and the fringe field capacitance between the plate element and the body is measured, to thereby determine the distance between the probe and the body surface. The probe may be in contact with and scanned across the body surface, to provide surface profile measurements. A probe including a plurality of plate elements may be positioned inside an opening such as a hole, to measure the geometry of the hole. By maintaining the hole probe adjacent one electrode in contact with the hole wall, both profile and geometry measurements may be made. A noncontacting probe including one or more plate elements may be used to measure surface topography.

Abstract: A probe for determining the thickness of an interface gap between two surfaces is disclosed. The probe includes an inflatable bladder, which can be inserted into a gap and inflated, such that the sides of the bladder contact the planes. A distance-measuring device is mounted within the cavity of the bladder and is suitable for measuring the distance between the sides of the bladder. Passive electrical circuitry for use as the distance-measuring device is also disclosed. Passive electrical circuitry has an electrical property that varies as the distance between the passive electrical elements varies. In the case of a probe utilizing capacitive circuitry, three relationally positioned measuring electrodes and a common electrode are mounted within the bladder cavity such that the measuring and common electrical are in facing relationship and move away from each other as the bladder is inflated. When the bladder is inflated with a dielectric fluid, the electrodes are pressed flat against the surfaces.

Abstract: A fringe field, capacitive distance sensor for measuring the distance between a probe and the surface of the conductive body. The sensor comprises a conductive plate element mounted by the probe, the thickness of the plate element being substantially less than the height and width of the plate element. The plate element is positioned adjacent to and normal to the body surface, and the fringe field capacitance between the plate element and the body is measured, to thereby determine the distance between the probe and the body surface. The probe may be in contact with and scanned across the body surface, to provide surface profile measurements. A probe including a plurality of plate elements may be positioned inside an opening such as a hole, to measure the geometry of the hole. By maintaining the hole probe adjacent one electrode in electrode in contact with the hole wall, both profile and geometry measurements may be made.