Ceramic resonance type electrostatic sensor apparatus

• US 5,231,359 A
• Filed: 05/18/1990
• Issued: 07/27/1993
• Est. Priority Date: 05/19/1989
• Status: Expired due to Term

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Sugimura, Takashi, Ohsawa, Tetsuo, Masuda, Noboru
• Primary Examiner(s): Harvey, Jack B.
• Assistant Examiner(s): Regan, Maura K.
• Application Number:
  US07/526,247
• Time in Patent Office: 1,166 Days
• Field of Search: 324/675, 324/681, 324/682, 324/72, 324/72.5, 324/458, 333/214, 333/215, 333/219.1
• US Class Current: 324/675
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence
• CPC Class Codes: G11B 9/06 using record carriers having variable electrical capacitance; Record carriers therefor G11B9/02 takes precedence

Abstract

A ceramic resonance type electrostatic sensor apparatus with an oscillator at a fixed frequency including a first ceramic resonator which has a fixed resonance frequency, a detecting unit for detecting a capacitance between the detecting unit and an object to be detected, a resonating circuit including a second ceramic resonator and having a resonance point which varies with the small change in capacitance detected by the detecting unit, a high impedance circuit connected between the oscillator and the resonating circuit, and a high impedance circuit connected between the resonating circuit and the detecting circuit.

Claims

1. A ceramic resonance type electrostatic sensor apparatus comprising an oscillator including a ceramic resonator, said first ceramic resonator having a fixed resonance frequency, and said oscillator to oscillate at a fixed frequency;

a detecting unit for detecting capacitance between said detecting unit and an object to be detected;

a resonating circuit including a second ceramic resonator and having a resonance point which varies with a small change in capacitance detected by said detecting unit, a high-impedance circuit connected between said oscillator and said resonating circuit and a high-impedance circuit connected between said resonating circuit and said detecting circuit thereby eliminating mutual interference between said oscillator and said resonating circuit.

2. The apparatus according to claim 1 wherein said first high-impedance circuit includes a transistor which is of an emitter-follower type connected to said second ceramic resonator of said resonating circuit.

3. The apparatus according to claim 1 wherein said second high-impedance circuit comprises a capacitor and an inductor connected to said second ceramic resonator of said resonating circuit.

4. The apparatus according to claim 1 wherein an AFC circuit having a reverse-biased variable capacitance diode is connected between said second ceramic resonator of said resonating circuit and said detecting circuit.

6. The apparatus according to claim 1 further comprising a ceramic substrate having a metal film on both a first and second surface of said ceramic substrate, said first and second ceramic resonators being arranged thereon.

7. The apparatus according to claim 6 wherein one of said ceramic resonators is arranged on one of said metal films, and the other of said ceramic resonators is arranged on the other of said metal films, thereby preventing an electric field of one of said ceramic resonators from interfering with the other of said ceramic resonators.

8. The apparatus according to claim 6 wherein both said ceramic resonators are arranged on the metal film on a same surface of said substrate is orthogonal directions.

9. The apparatus according to claim 6 wherein a positive side line of a power source and signal line are arranged on the first surface of said ceramic substrate and separated ground lines are formed on said second surface of said ceramic substrate and an inductance coil is connected between said separated ground lines.

5. A ceramic resonance type electrostatic sensor apparatus comprising:

an oscillator adapted for oscillating at a fixed frequency, including a first ceramic resonator having a fixed resonance point;

a detecting unit for detecting capacitance between said detecting unit and an object to be detected;

a C-L converter for converting the capacitance detected by said detecting unit into inductance;

a resonating circuit including a second resonator having a resonance point which varies with a small change in inductance output from said C-L converter; and

a high-impedance circuit connected between said oscillator and said resonating circuit and a high-impedance circuit connected between said resonating circuit and said detecting circuit.

10. A ceramic resonance type electrostatic sensor apparatus comprising a variable capacitance diode connected to said ceramic resonator through a capacitor, a variable potential converter for variably adjusting an operating voltage to be applied to said variable capacitance diode, and a high frequency separating circuit connected between said variable potential converter;

and wherein said oscillator includes a first ceramic resonator, said first ceramic resonator having a fixed resonance frequency, and said oscillator is adapted to oscillate at a fixed frequency;

a detecting unit for detecting a capacitance between said detecting unit and an object to be detected;

a resonating circuit including a second ceramic resonator and having a resonance point which varies with the small change in capacitance detected by said detecting unit, and high-impedance circuits for respectively connecting to input and output stages of said second ceramic resonator of said resonating circuit thereby eliminating mutual interference between said oscillator and said resonating circuit.

11. The apparatus according to claim 10 wherein said variable potential converter comprises a variable resistor.

12. The apparatus according to claim 10 wherein said high frequency separating circuit comprises a resistor having a high resistance.

13. The apparatus according to claim 10 wherein said high frequency separating circuit comprises a high impedance coil.

14. The apparatus according to claim 10 further comprising an elongated lead means for connection between said high frequency separating circuit and said variable potential converter.

15. The apparatus according to claim 14 further comprising capacitors for connecting both end portions of said lead means thereby grounding capacitance components and inductance components which are formed on the lead means.

16. A dielectric resonance type electrostatic sensor apparatus, comprising:

an oscillator including a first dielectric resonator for oscillating at a predetermined frequency;

a detecting means for detecting a capacitance between said detecting means and an object to be detected;

a resonating circuit including a second dielectric resonator and having a resonance frequency which is shifted with the small change in capacitance detected by said detecting means;

a high-impedance converter for connecting between said oscillator and said resonating circuit whereby eliminating mutual interference between said oscillator and said resonating circuit;

a detecting circuit for detecting an output from said resonating circuit; and

a high-impedance circuit for connection between said resonating circuit and said detecting circuit.

17. The apparatus according to claim 16 wherein said high-impedance converter comprises a high impedance circuit.

18. The apparatus according to claim 17 wherein said high-impedance circuit includes a transistor which is of an emitter follower type connected to said resonating circuit.

19. The apparatus according to claim 16 wherein said high-impedance circuit comprises a coupling capacitor connected between said resonating circuit and said detecting circuit and an inductance element coupled to said capacitor so as to constitute an LC resonator.

20. The apparatus according to claim 19 wherein said inductance element is connected in parallel with said second dielectric resonator.

21. The apparatus according to claim 19 wherein said inductance element is connected in series with said coupling capacitor.

22. A dielectric resonance type electrostatic sensor apparatus, comprising:

an oscillator including a first dielectric resonator for oscillating at a predetermined frequency;

a detecting means for detecting a capacitance between said detecting means and an object to be detected;

a resonating circuit including a second dielectric resonator and having a resonance frequency which is changed with the small change in capacitance detected by said detecting means;

a high impedance converter for connecting between said oscillator and said resonating circuit, thereby eliminating mutual interference between said oscillator and said resonating circuit;

a detecting circuit for detecting an output from said resonating circuit;

an AFC circuit for connection between said resonating circuit and said detecting circuit; and

a high impedance circuit for connection between said resonating circuit and said detecting circuit.

23. The apparatus according to claim 22 wherein said high-impedance circuit comprises a coupling capacitor connected between said resonating circuit and said detecting circuit and an inductance element coupled to said capacitor so as to constitute an LC resonator.

24. The apparatus according to claim 22 wherein said AFC circuit comprises a reverse-biased variable capacitance diode which varies the resonance frequency of said resonating circuits.