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:
May. 11, 2004
Filed:
Jun. 13, 2002
Michael W. Fortner, Plano, TX (US);
Mykrolis Corporation, Billerica, MA (US);
Abstract
Systems and methods for determining differential currents in a pair of circuits. In a preferred embodiment, an excitation voltage and a tightly coupled differencing current transformer are coupled to a differential capacitance manometer to generate a differential current. This differential current is input to a low-impedance summing node of a charge amplifier that effectively integrates the differential current. A shielding structure surrounding the current transformer and amplifier is driven to the excitation voltage potential. The output of the charge amplifier is passed through a common mode transformer which is coupled to the excitation voltage source in order to remove the guard potential (corresponding to the excitation signal) from the output signal. A synchronous detector then converts the resulting signal to a DC level indicative of the differential capacitance of the sensor.