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. 13, 2004
Filed:
Feb. 15, 2002
Rongtai Wang, Edina, MN (US);
Rosemount Inc., Eden Prairie, MN (US);
Abstract
A pair of sensing capacitors, each having a capacitance C and C respectively, based on a process variable, are coupled to a bridge node which is coupled to a summing node. A reference capacitor, coupled to the summing node, has a capacitance C greater than an expected maximum difference between the capacitances of the pair of sensing capacitors. Switches selectively couple the sensing capacitors and the reference capacitor to at least first and second voltages to derive charges representative of C -C and C . In one embodiment the sensing capacitors are operated to charge and discharge during respective first and second phases of first cycles and the reference capacitor is operated to charge and discharge during respective first and second phases of second cycles. In another embodiment, the reference capacitor is operated to charge and discharge during alternate phases of the first and second cycles and the sensing capacitors are operated to charge and discharge during respective first and second phases of all cycles.