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. 03, 1983
Filed:
Jan. 23, 1981
James R Ruesch, Boulder, CO (US);
Roger L Frick, Eden Prairie, MN (US);
Earl A Grindheim, Richfield, MN (US);
Rosemount Inc., Eden Prairie, MN (US);
Abstract
A circuit for measuring the reactance of an AC reactance sensor which varies responsive to a condition to be sensed, such as pressure, is disclosed. The circuit comprises an oscillator coupled to the sensor for providing a time varying oscillator signal having a variable frequency and a substantially constant peak to peak voltage to the sensor, and a plurality of rectifiers coupled to the oscillator and to the sensor for providing the oscillator signal as a charging signal to the sensor and for providing discharging signals from the sensor, the discharging signals being a function of the reactance of the sensor, and an amplifier coupled to the rectifiers and to the oscillator for providing an input control signal to the oscillator to control the frequency of the oscillator signal as a function of the reactance of the sensor.