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:
Dec. 04, 2001
Filed:
Oct. 08, 1999
Toshiyuki Matsumoto, Hyogo-ken, JP;
Yoshihiro Hirota, Kyoto, JP;
Muneo Harada, Hyogo-ken, JP;
Takaya Miyano, Aomori-ken, JP;
Sumitomo Metal Industries, Ltd., Osaka, JP;
Abstract
A detection circuit which is capable of outputting a voltage proportional to a static capacitance of a sensor is provided, which comprises a voltage input terminal connected to receive an input voltage and an operational amplifier. The input voltage received at the voltage input terminal is changed between two different reference voltages. An inverting input terminal of the amplifier is connected to the voltage input terminal through a resistor, and a non-inverting input terminal of the amplifier is connected to the voltage input terminal through the sensor capacitance and to one of the reference voltages through a switch. An output voltage of the amplifier is connected to the inverting input terminal through a feedback circuit including a resistor and a switch. The switches are closed and the one of the reference voltages is supplied to the input terminal during an initialization cycle. The switches are opened and the other reference voltage is supplied to the input terminal during a measurement cycle. The operational amplifier outputs an output voltage which linearly varies in response to the sensor capacitance.