Capacitive physical quantity sensor and method of diagnosing the same
First Claim
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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 includingan 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, anda time measuring means for measuring a time period, for which the instruction signal is input into the input terminal, whereinthe 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, andthe predetermined time is between 0.1 and 0.5 ms.
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Abstract
A capacitive sensor for detecting a physical quantity includes 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 includes an input terminal, an output terminal, and a time measuring means for measuring a time period. The controlling unit measures the time period, for which a diagnosis instruction signal is input into the input terminal. The controlling unit performs the self-diagnosis, after the instruction signal continues for a predetermined time period.
37 Citations
12 Claims
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1. A capacitive sensor for detecting a physical quantity, the sensor comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A capacitive sensor for detecting a physical quantity, the sensor comprising:
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a single sensing element including a movable electrode and a fixed electrode and responding to a physical quantity applied thereto when a periodic signal is applied thereto; a signal processing circuit connected to the single sensing element to produce a sensor signal corresponding to a responding operation of the single sensing clement; a first output terminal connected to the signal processing circuit for outputting a processed signal of the signal processing circuit; a branch circuit connected to the signal processing circuit for amplifying the processed signal; a second output terminal connected to the branch circuit for outputting an amplified signal of the branch circuit; an input terminal for receiving a self-diagnosis instruction signal from an external side; a control circuit connected to the input terminal for controlling the single sensing element and the signal processing circuit to perform a self-diagnosis operation in response to the self-diagnosis instruction signal; and an internal clock generator for supplying internal clocks for timing operations of the control circuit, wherein all the single sensing element, the signal processing circuit, the first output terminal, the branch circuit, the second output terminal, the input terminal, the control circuit and the internal clock generator are integrated in a single circuit piece. - View Dependent Claims (10)
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11. A method of diagnosing a capacitive physical quantity sensor comprising:
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inputting a preparation signal into an input terminal of the capacitive physical quantity sensor for a first predetermined time; determining whether an output terminal of the capacitive physical quantity sensor has output a first output signal for the first predetermined time or not in response to the preparation signal; instructing a self-diagnosis by inputting art instruction signal into the input terminal for a second predetermined time;
if the output terminal is determined to have output the first output signal for the first predetermined time; anddiagnosing the capacitive physical quantity sensor to be normal, if the output terminal outputs a second output signal for the Second predetermined time, wherein the output terminal is a first output terminal, and the capacitive physical quantity sensor includes a second output terminal the capacitive physical quantity sensor has a first sensitivity and a second sensitivity for a single direction. the first output terminal outputs a signal of the first sensitivity, the method includes amplifying the signal of the first sensitivity to produce a signal of a second sensitivity; the second output terminal outputs the signal of the second sensitivity, and the diagnosing is performed based on a time, for which the signal of the second sensitivity continues. - View Dependent Claims (12)
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Specification