Resonant gauge with microbeam driven in constant electric field
US5275055A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 31, 1992 |
| Grant date | Jan 4, 1994 |
| Priority date | — |
| Expiry date | Aug 31, 2012 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S73/01
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A resonant strain gauge includes a silicon substrate, a polysilicon flexure beam attached at both ends to the substrate, and a polysilicon rigid cover cooperating with the substrate to enclose the flexure beam within a sealed vacuum chamber. An upper bias electrode is formed on the cover, and a lower bias electrode is formed on the substrate directly beneath and spaced apart from the flexure beam. A drive electrode is formed in or on the beam, centered between the upper and lower bias electrodes transversely with respect to the direction of beam elongation. The upper and lower electrodes are biased at constant voltage levels, of equal magnitude and opposite polarity. The drive electrode, ordinarily biased at ground, is selectively charged by applying an oscillating drive voltage, to cause mechanical oscillation of the beam. A piezoresistor element, formed on the beam, senses beam oscillation and provides a position indicating input to the oscillator circuit that drives the beam. The beam tends to oscillate at its natural resonant frequency. The piezoresistor thus provides the natural resonant frequency to the oscillating circuit, adjusting the frequency of the beam drive signal tow…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.