| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable capacitance measuring apparatus which is easily integrated, extremely low in power consumption, and suitable for downsizing. SOLUTION: An SAR-type A/D converter is utilized, and an electric charge is measured in place of a voltage. The operation of charging at an initial stage differs from that of the SAR-type A/D converter, and only a capacitive pressure sensor is charged. A capacitance offset canceling circuit is disposed in order to properly detect a change in capacitance. COPYRIGHT: (C)2009,JPO&INPIT |
