Abstract: A silicon capacitive pressure sensor is disclosed that has a glass dielectric material sputter-deposited onto a silicon substrate of the sensor. After deposition of the bulk dielectric material, the glass is patterned and etched to form a pair of concentric rings. An inner ring is of a circular shape, while the outer ring is of an octagonal shape. As compared to prior art dielectric spacers which are of a single ring of relatively wide thickness, the pair of concentric rings disclosed herein significantly reduce the parasitic capacitance of the glass dielectric material, thereby increasing the sensitivity of the sensor.

Abstract: A dual-element, parallel-plate silicon capacitative pressure sensor includes a pressure sensing element and a reference element of identical structure. Both elements are separately fabricated from the same silicon wafers using identical processing steps. Further, both elements are simultaneously mounted to a header using identical mounting steps. Such identical fabrication and mounting steps serve to identically match the dielectric materials and, thus, the aging properties of both the sensing and reference elements. By matching the sensing and reference elements in these ways, and by aging these components at elevated temperatures in exactly the same way, it is possible to achieve an extremely close match in long-term dielectric aging properties.

Abstract: A dual-element, parallel-plate silicon capacitative pressure sensor includes a pressure sensing element and a reference element of identical structure. Both elements are fabricated from the same silicon wafers using identical processing steps. Further, both elements are simultaneously mounted to a header using identical mounting steps. Such identical fabrication and mounting steps serve to identically match the dielectric materials and, thus, the aging properties of both the sensing and reference elements. By matching the sensing and reference elements in these ways, and by aging these components at elevated temperatures in exactly the same way, it is possible to achieve an extremely close match in long-term dielectric aging properties.

Abstract: A silicon capacitive pressure sensor is disclosed having a silicon substrate and a silicon diaphragm separated by a glass dielectric spacer. The substrate has an upper surface formed as a mesa which is generally curved in shape, the curvature being concave. Due to manufacturing constraints the mesa upper surface comprises a series of concentric rings that approximate the desired concave shape. The step height and diameter of the rings are such that, at full deflection of the diaphragm, the diaphragm touches the center of the mesa, but not the edges of the individual steps. That is, letting the edges or corners of the steps define a curve, the radius of curvature of the diaphragm is smaller than the radius of curvature of the locus of the step corners.

Abstract: Apparatus for externally welding a seam along abutting lengths of pipe with the pipe being supported on site in position, e.g., on the ground, the apparatus having laser transmitting means which includes optically coupled individual reflectors supported for orbital movement about the seam, the optically coupled individual reflectors serving to provide a folded multiple reflection path to the seam for transmitting a focused laser beam onto the seam along a predetermined section thereof below the pipe axis.