Patent ID: 7432724
Filing Date: 2008-10-07
Classification: G01D,G01P,G01R

Abstract:
1. A capacitive sensor for detecting a physical quantity, the sensor comprising: a movable electrode and a fixed electrode; and a controlling unit for applying a signal between the movable electrode and the fixed electrode, the controlling unit including an input terminal, into which an instruction signal for instructing a self-diagnosis is input, an output terminal, which outputs an indication signal for indicating a state of the self-diagnosis, and a time measuring means for measuring a time period, for which the instruction signal is input into the input terminal, wherein the controlling unit performs the self-diagnosis, after the instruction signal continues for a predetermined time period, the time measuring means measures the time period by using a clock for generating clock signals; the predetermined time period corresponds to a time longer than a time for which it is assumed that external noise will continue, the sensor is included in an automobile, and the predetermined time is between 0.1 and 0.5 ms.