Phase discriminating capacitive array sensor system

• US 5,214,388 A
• Filed: 05/28/1992
• Issued: 05/25/1993
• Est. Priority Date: 05/28/1992
• Status: Expired due to Term

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Rahim, Wadi, Vranish, John M.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US07/889,577
• Time in Patent Office: 362 Days
• Field of Search: 324/660, 324/662, 324/681, 324/683, 324/687, 324/690, 340/870.37
• US Class Current: 324/683
• CPC Class Codes: G01D 5/2405 by varying dielectric
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard

Abstract

A phase discriminating capacitive sensor array system which provides multiple sensor elements which are maintained at a phase and amplitude based on a frequency reference provided by a single frequency stabilized oscillator. Sensor signals provided by the multiple sensor elements are controlled by multiple phase control units, which correspond to the multiple sensor elements, to adjust the sensor signals from the multiple sensor elements based on the frequency reference. The adjustment made to the sensor signals is indicated by output signals which indicate the proximity of the object. The output signals may also indicate the closing speed of the object based on the rate of change of the adjustment made, and the edges of the object based on a sudden decrease in the adjustment made.

Claims

1. A phase discriminating capacitive sensor array system for detecting an object, comprising:

(a) a capacitive sensor array having sensor elements to sense the object, each sensor element producing a sensor signal;

(b) a frequency stabilized oscillator providing a frequency reference; and

(c) phase control means for controlling a phase and amplitude of each sensor signal, and adjusting each sensor signal to correspond to the frequency reference provided by said frequency stabilized oscillator.

2. A phase discriminating capacitive sensor array system according to claim 1, wherein

said phase control means produces an output signal indicating a proximity of the object based on the adjustment made to each said sensor signal by said phase control means.

3. A phase discriminating capacitive sensor array system according to claim 1, wherein

said phase control means produces an output signal indicating an edge of the object based on a sudden decrease in the adjustment made to the sensor signal.

4. A phase discriminating capacitive sensor array system according to claim 1, wherein said capacitive sensor array comprises a shield on which said sensor elements are provided.

5. A phase discriminating capacitive sensor array system for detecting an object, comprising:

(a) a capacitive sensor array having sensor elements to sense the object, each sensor element producing a sensor signal;

(b) a frequency stabilized oscillator providing a frequency reference; and

(c) a phase control means for controlling a phase and amplitude of each sensor signal, and adjusting each sensor signal to correspond to the frequency reference provided by said frequency stabilized oscillator;

said phase control means producing an output signal indicating a closing speed of the object based on a rate of change of the adjustment made to the sensor signal.

6. A method of detecting an object, comprising the steps of:

(a) sensing the object with multiple sensor elements and producing a sensor signal for each of the sensor elements;

(b) providing a common frequency reference for each of the sensor elements; and

(c) adjusting the phase and amplitude of the sensor signal from each of the sensor elements to correspond to the common frequency reference.

7. A method according to claim 6, further comprising the step of

(d) producing an output signal indicating a proximity of the object based on the adjustment made to each said sensor signal.

8. A method according to claim 6, further comprising the step of:

(d) producing an output signal indicating an edge of the object based on a sudden decrease in the adjustment made to the sensor signal.

9. A method according to claim 6, wherein step (c) comprises

adjusting a voltage indicating initial sensor voltage by a voltage change induced by an amplitude change caused by sensing the object, and adjusting a voltage indicating initial sensor voltage by a voltage change induced by a phase change caused by sensing the object.

10. A method according to claim 9, wherein step (d) comprises

producing an output signal indicating a proximity of the object based on the adjustment made to each said sensor signal based on the adjusted voltage.

11. A method according to claim 9, wherein step (d) comprises

producing an output signal indicating a closing speed of the object based on a rate of change of the adjustment made to the sensor signal.

12. A method according to claim 9, wherein step (d) comprises

producing an output signal indicating an edge of the object based on a sudden decrease in the adjustment made to the sensor signal based on the adjusted voltage.

13. A method of detecting an object, comprising the steps of:

(a) sensing the object with multiple sensor elements and producing a sensor signal for each of the sensor elements;

(b) providing a common frequency reference for each of the sensor elements;

(c) adjusting the phase and amplitude of the sensor signal from each of the sensor elements to correspond to the common frequency reference; and

(d) producing an output signal indicating a closing speed of the object based on a rate of change of the adjustment made to the sensor signal.