Title:
CAPACITANCE DETECTION SYSTEM AND METHOD
Document Type and Number:
WIPO Patent Application WO1999042848
Kind Code:
A3
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 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.
Inventors:
MATSUMOTO TOSHIYUKI (JP)
HIROTA YOSHIHIRO (JP)
HARADA MUNEO (JP)
MIYANO TAKAYA (JP)
HIROTA YOSHIHIRO (JP)
HARADA MUNEO (JP)
MIYANO TAKAYA (JP)
Application Number:
PCT/JP1999/000736
Publication Date:
November 25, 1999
Filing Date:
February 19, 1999
Export Citation:
Assignee:
SUMITOMO METAL IND (JP)
MATSUMOTO TOSHIYUKI (JP)
HIROTA YOSHIHIRO (JP)
HARADA MUNEO (JP)
MIYANO TAKAYA (JP)
MATSUMOTO TOSHIYUKI (JP)
HIROTA YOSHIHIRO (JP)
HARADA MUNEO (JP)
MIYANO TAKAYA (JP)
International Classes:
G01D5/241; G01D5/24; G01H11/06; G01L9/12; G01R27/26; H04R5/04; (IPC1-7): G01R27/26
Foreign References:
| DE3413849A1 | 1985-08-22 | |||
| DE4135991C1 | 1992-12-17 |
Other References:
PATENT ABSTRACTS OF JAPAN vol. 18, no. 519 (P - 1807) 29 September 1994 (1994-09-29)
Download PDF: