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:
Feb. 04, 1992
Filed:
Feb. 07, 1990
Gabriel L Miller, Westfield, NJ (US);
Eric R Wagner, South Plainfield, NJ (US);
AT&T Bell Laboratories, Murray Hill, NJ (US);
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.