Capacitive force-balance system for measuring small forces and pressures
US5085070A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 7, 1990 |
| Grant date | Feb 4, 1992 |
| Priority date | — |
| Expiry date | Feb 7, 2010 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S977/863
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A force balancing method and apparatus detects small changes in force or pressure. An LC tuned circuit having a capacitor with at least one movable plate senses force or pressure changes. Deviations in the phase of the response of the tuned circuit are compared to the phase of a driving reference oscillator to generate an error signal. The error signal is used to control the oscillator to increase or decrease its output amplitude for driving the tuned circuit. As a result the electrostatic force across the capacitor plates tends to change in such a way as to precisely balance the effect of external force or pressure changes. The system therefore operates in a force-balance mode and in such a way as to provide a high sensitivity together with a precisely controlled stiffness. This system is particularly applicable to high sensitivity microphones, micro-topography, and atomic force microscopy.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.