Force responsive capacitive transducer

• US 4,719,538 A
• Filed: 12/02/1986
• Issued: 01/12/1988
• Est. Priority Date: 12/02/1986
• Status: Expired due to Fees

• Current Assignee: John D. Cox
• Original Assignee: John D. Cox
• Inventors: Cox, John D.
• Primary Examiner(s): Griffin, Donald
• Application Number:
  US06/936,893
• Time in Patent Office: 406 Days
• Field of Search: 361/283, 73/718, 73/724
• US Class Current: 361/283.2
• CPC Class Codes: G01D 5/2417 by varying separation
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence
• CPC Class Codes: G01L 5/165 using variations in capacitance
• CPC Class Codes: G01L 5/223 to joystick controls
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass
• CPC Class Codes: G01L 9/125 with temperature compensating means non electric temperature compensating means G01L19/04

Abstract

A capacitive transducer includes a plurality of first electrodes which, together with at least one second electrode, define a plurality of capacitors having capacitance variable with spacing. An actuator element connected to a plate supporting at least one second electrode angularly deflects the plate. This angular deflection causes the spacing, and thus the capacitance, of electrode sets disposed on opposite sides of the center of the plate to vary in a differential manner.

Claims

1. A force-responsive capacitive transducer, comprising:

first electrode means including a plurality of electrode regions;

second electrode means spaced apart from the first electrode means and angularly deflectable in response to applied moment, for defining with the first electrode means a plurality of capacitors having capacitance variable with spacing, such spacing being differentially variable with angular deflection of said second electrode means;

actuator means connected to said second electrode means and responsive to externally applied force, for applying moment to said second electrode means and varying the spacing between said first and second electrode means, whereby capacitance is varied; and

diaphragm means, connected to said second electrode means, for elastically deflecting in response to moment applied to said second electrode means.

2. A transducer according to claim 1, wherein the first electrode means has a center and the electrode regions define a substantially symmetrical array of sectors about the center.

3. A transducer according to claim 1, further comprising:

signal generating means responsive to the variable capacitance of the force to capacitance transducer means, for generating signals representative of force variations.

4. A transducer according o claim 3 wheein the signal generating means comprises first and second variable frequency oscillator means, each coupled to the transducer means and responsive to the capacitive value of each for providing first and second variable frequency signals representative of applied momemt;

and

means responsive to said first and second variable frequency signals for generating a third variable frequency signal representative of the difference between said first and second variable frequency signals.

5. A transducer according to claim 3, further comprising digital processor means, connected to said signal generating means, for controlling the signal generating means and processing signals generated by the signal generating means.

6. A force-responsive capacitive transducer, comprising:

flexible diaphragm means deflectable in response to a centrally applied moment, said flexible diaphragm means including first electrode means, such electrode means having at least two electrode regions;

second electrode means spaced apart from said first electrode means for defining with the first electrode means a plurality of capacitors having capacitance variable with spacing; and

actuator means for applying moment, connected to the flexible diaphragm means so that applied moment deflects the flexible diaphragm means and varies the spacing between the flexible diaphragm means and the second electrode means, whereby capacitance is varied.

7. A transducer according to claim 6, wherein the flexible diaphragm means has a center and the electrode regions define a substantially symmetrical array of plush sectors about the center of said diaphragm.

8. A transducer according to claim 6, further comprising:

signal generating means responsive to the variable capacitance of the force to capacitance transducer means, for generating signals representative of force variations.

9. A force-responsive capacitive transducer comprising:

flexible diaphragm means deflectable in response to a centrally applied moment, said flexible diaphragm means including first electrode means, such electrode means having at least two electrode regions;

second electrode means spaced apart from said first electrode means for defining with the first electrode means a plurality of capacitors having capacitance variable with spacing;

actuator means for applying moment, connected to the flexible diaphragm means so that applied moment deflects the flexible diaphragm means and varies the spacing between the flexible diaphragm means and the second electrode means, whereby capacitance is varied; and

signal generating means responsive to the variable capacitance of the force to capacitance transducer means, for generating signals representative of force variations, the signal generating means including

first and second variable frequency oscillator means, each coupled to the transducer means and responsive to the capacitive value of each for providing first and second variable frequency signals representative of applied moment; and

means responsive to said first and second variable frequency signals for generating a third variable frequency signal representative of the difference between said first and second variable frequency signals.

10. A force-responsive capacitive transducer comprising

flexible diaphragm means deflectable in response to a centrally applied moment, said flexible diaphragm means including first electrode means, such electrode means having at least two electrode regions;

second electrode means spaced apart from said first electrode means for defining with the first electrode means a plurality of capacitors having capacitance variable with spacing;

actuator means for applying moment, connected to the flexible diaphragm means so that applied moment deflects the flexible diaphragm means and varies the spacing between the flexible diaphragm means and the second electrode means, whereby capacitance is varied;

signal generating means responsive to the variable capacitance of the force to capacitance transducer means, for generating signals representative of force variations; and

digital processor means, connected to said signal generating means, for controlling the signal generating means and processing signals generated by the signal generating means.

11. A capacitive transducer for converting applied force to capacitive changes, comprising:

a substantially rigid support element;

a flexible diaphragm having a relatively rigid central region and a peripheral region affixed to said support element;

a plurality of first electrodes mounted on said flexible diaphragm;

actuator means attached to said central region of said flexible diaphragm;

second electrode means spaced apart from and affixed to said rigid central region of said diaphragm, for defining with said first electrode means an arrangement of capacitors, said capacitors having capacitance variable with spacing, and

so that angular deflection of the central region of the diaphragm relative to said support element differentially varies the spacings of said capacitors, whereby capacitance is varied and applied force is measured.

12. A transducer according to claim 11, wherein said plurality of first electrodes are mounted on said substantially rigid peripheral support.

13. A transducer according to claim 12, wherein ones of said plurality of first electrodes are also mounted on said flexible diaphragm.