The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 12, 1988
Filed:
Dec. 20, 1985
John C Cole, Mercer Island, WA (US);
Silicon Designs, Inc., Bellevue, WA (US);
Abstract
The accelerometer comprises a substrate (52), a metallic movable plate (50), and a mounting system (54) for mounting the movable plate such that it is positioned above the substrate and can rotate about a flexure axis (64) that is above and is substantially parallel to the substrate. The flexure axis divides the sensing element into first (66) and second (68) sections. The total moments of the first and second sections about the flexure axis are different, such that acceleration normal to the substrate tends to rotate the sensing element about the flexure axis. A first electrode (74) is mounted by the substrate adjacent the first section to form a first capacitor (C.sub.A), and a second electrode (76) is mounted by the substrate adjacent the second section to form a second capacitor (C.sub.B). A detector for measuring the relative capacitances of the first and second capacitors is provided comprising an integrator (166), an inverting amplifier (168), and switches (160, 162, 164) for periodically charging and discharging the capacitors in response to a clock signal. In one embodiment, the sensing element includes an internal opening (16, 56, 126) and the mounting system is positioned within the opening and includes a pedestal mounted to the substrate, and torsion bars (20, 22, 118, 120) and/or a beam (60, 114) connecting the pedestal to the sensing element. The sensing element preferably comprises a metallic plate, and the substrate preferably comprises a semiconductor upon which the detector and electrodes are fabricated in a single step process requiring no final assembly of components. In an embodiment adapted for high g applications, a pedestal (146) divides a plate member into first (148) and second (150) cantilevered beams that flex in the same direction in response to a given acceleration.