Capacitive sensor apparatus

• US 6,744,258 B2
• Filed: 07/08/2002
• Issued: 06/01/2004
• Est. Priority Date: 07/11/2001
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Shimaoka, Keiichi, Funabashi, Hirofumi, Ohta, Norikazu, Makino, Yasuaki, Ito, Hajime, Suzuki, Yasutoshi, Ishio, Seiichiro
• Primary Examiner(s): Hirshfeld, Andrew H.
• Assistant Examiner(s): NGUYEN, HOAI AN D
• Application Number:
  US10/189,565
• Publication Number:
  US 20030011378A1
• Time in Patent Office: 694 Days
• Field of Search: 324/548, 324/658, 324/660, 324/71.1, 324/661, 324/378, 324/403, 324/415, 324/425, 324/500, 324/537, 327/95, 327/554, 361/118, 737/18
• US Class Current: 324/548
• CPC Class Codes: G01D 3/08 with provision for safeguarding the apparatus, e.g. against abnormal operation, against breakdown

Abstract

In a capacitive sensor apparatus, a capacitive sensor includes a plurality of physical-quantity-detection capacitors each having a movable electrode and a fixed electrode. A conversion device operates for converting an output signal of the capacitive sensor into an apparatus output signal. Each of the physical-quantity-detection capacitors is selectively connected and disconnected to and from the conversion device. A determination is made as to whether or not each of the physical-quantity-detection capacitors fails in response to the sensor output signal. When it is determined that a first one of the physical-quantity-detection capacitors fails, the first one is disconnected from the conversion device and a second one of the physical-quantity-detection capacitors is connected to the conversion device.

Claims

1. A capacitive sensor apparatus comprising:

a capacitive sensor including a plurality of physical-quantity-detection capacitors each having a movable electrode and a fixed electrode;

a conversion device for converting an output signal of the capacitive sensor into an apparatus output signal;

first means for selectively connecting and disconnecting each of the plurality of physical-quantity-detection capacitors to and from the conversion device;

second means for determining whether or not each of the plurality of physical-quantity-detection capacitors fails in response to the capacitive sensor output signal; and

third means for, when the second means determines that a first one of the plurality of physical-quantity-detection capacitors fails, disconnecting the first one from the conversion device and connecting a second one of the plurality of physical-quantity-detection capacitors to the conversion device,

wherein the conversion device includes means for changing a characteristic of the conversion of the output signal of the capacitive sensor into the apparatus output signal in accordance with which one of the plurality of physical-quantity-detection capacitors is connected to the conversion device to make the apparatus output signal independent of which one of the plurality of the physical-quantity-detection capacitors is connected to the conversion device.

2. A capacitive sensor apparatus as recited in claim 1, wherein the means in the conversion device changes a gain of the conversion of the output signal of the capacitive sensor into the apparatus output signal in accordance with which of the physical-quantity-detection capacitors is connected to the conversion device.

3. A capacitive sensor apparatus as recited in claim 1, wherein the movable electrode of each of the plurality of physical-quantity-detection capacitors is formed on a portion of one of a diaphragm, a plurality of diaphragms, a mass, and a plurality of masses.

4. A capacitive sensor apparatus as recited in claim 3, wherein one of the plurality of physical-quantity-detection capacitors fails when an amount of deformation of the diaphragm is outside a prescribed range.

5. A capacitive sensor apparatus as recited in claim 1, wherein the conversion device further comprises at least one feedback capacitor having an upper electrode and a lower electrode and being selected in accordance with the one of the plurality of physical-quantity-detection capacitors connected to the conversion device independent of the apparatus output signal.

6. A capacitive sensor apparatus comprising:

a capacitive sensor including a plurality of physical-quantity-detection capacitors each having a movable electrode and a fixed electrode;

a conversion device for converting an output signal of the capacitive sensor into an apparatus output signal;

first means for selectively connecting and disconnecting each of the plurality of physical-quantity-detection capacitors to and from the conversion device;

second means for determining whether or not each of the plurality of physical-quantity-detection capacitors fails in response to the capacitive sensor output signal;

third means for, when the second means determines that a first one of the plurality of physical-quantity-detection capacitors fails, disconnecting the first one from the conversion device and connecting a second one of the plurality of physical-quantity-detection capacitors to the conversion device;

fourth means for applying a detection-purpose voltage to the capacitive sensor; and

fifth means for changing the applied detection-purpose voltage in accordance with which one of the plurality of physical-quantity-detection capacitors is connected to the conversion device to make the apparatus output signal independent of which one of the plurality of the physical-quantity-detection capacitors is connected to the conversion device.

7. A capacitive sensor apparatus as recited in claim 6, wherein the conversion device further comprises at least one feedback capacitor having an upper electrode and a lower electrode and being selected in accordance with the one of the plurality of physical-quantity-detection capacitors connected to the conversion device independent of the apparatus output signal.

8. A capacitive sensor apparatus comprising:

first and second capacitors having capacitances depending on a physical quantity to be detected;

first means for detecting the physical quantity in response to the capacitance of the first capacitor;

second means for determining whether or not the first capacitor fails;

third means for, in cases where the second means determines that the first capacitor fails, detecting the physical quantity in response to the capacitance of the second capacitor;

fourth means for applying a detection-purpose voltage to the first and second capacitors; and

fifth means for changing the applied detection-purpose voltage in accordance with which one of the first and second capacitors is used to detect the physical quantity to make a signal value of the detected physical quantity independent of which one of the first and second capacitors is used to detect the physical quantity.

9. A capacitive sensor apparatus as recited in claim 8, wherein the conversion device further comprises at least one feedback capacitor having an upper electrode and a lower electrode and being selected in accordance with the one of the plurality of physical-quantity-detection capacitors connected to the conversion device independent of the apparatus output signal.

10. A capacitive sensor apparatus, comprising:

a capacitive sensor including a plurality of physical-quantity-detection capacitors each having a movable electrode and a fixed electrode;

a conversion circuit for converting an output signal of the capacitive sensor into an apparatus output signal;

a control circuit for selectively connecting and disconnecting each of the plurality of physical-quantity-detection capacitors to and from the conversion device; and

a decision circuit for determining whether or not each of the plurality of physical-quantity-detection capacitors fails in response to the capacitive sensor output signal,

wherein the control circuit is for, when the decision circuit determines that a first one of the plurality of physical-quantity-detection capacitors fails, disconnecting the first one of the plurality of physical-quantity-detection capacitors from the conversion circuit and connecting a second one of the plurality of physical-quantity-detection capacitors to the conversion circuit, and

the conversion circuit further is for changing a characteristic of the conversion of the output signal of the capacitive sensor into the apparatus output signal in accordance with which one of the plurality of physical-quantity-detection capacitors is connected thereto to make the apparatus output signal independent of which one of the plurality of the physical-quantity-detection capacitors is connected to the conversion circuit.