LC resonance circuit displacement sensor

• US 5,760,577 A
• Filed: 04/19/1996
• Issued: 06/02/1998
• Est. Priority Date: 04/20/1995
• Status: Expired due to Fees

• Current Assignee: Techno Excel Kabushiki Kaisha
• Original Assignee: Techno Excel Kabushiki Kaisha
• Inventors: Shizuya, Yoshihiro
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US08/634,928
• Time in Patent Office: 774 Days
• Field of Search: 324/207.16, 324/207.24, 324/207.26, 324/207.17, 324/207.18, 324/207.22, 73/313, 73/314, 73/514.31, 73/514.38, 73/722, 73/728, 177/210 EM, 367/178, 340/686, 340/690
• US Class Current: 324/207.16
• CPC Class Codes: G01B 7/00 Measuring arrangements characterised by the use of electric or magnetic techniques
• CPC Class Codes: G01F 23/20 by measurement of weight, e.g. to determine the level of stored liquefied gas
• CPC Class Codes: G01L 9/007 using variations in inductance
• CPC Class Codes: G01L 9/10 by making use of variations in inductance , i.e. electric circuits therefor
• CPC Class Codes: G01P 13/00 Indicating or recording presence, absence, or direction, of movement electric switches H01H; counting moving objects G06M7/00
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values
• CPC Class Codes: G01P 3/4802 by using electronic circuits in general

Abstract

The present invention is a displacement sensor, which is capable of keeping high sensing resolution even if the amount of displacement of the core and the amount of changing the inductance are small. In the displacement sensor of the present invention, a displacing body is capable of displacing according to external force. An LC resonance circuit includes a magnetic coil and a core made of a magnetizable material, which is capable of moving close to and away from the magnetic coil according to the displacement of the displacing body. An oscillator inputs continuous signals having prescribed frequency to the LC resonance circuit. A detecting circuit detects the amount of the displacement of the displacing body on the basis of amplitude of the continuous signals from the LC resonance circuit.

Claims

1. A displacement sensor comprising:

a displacing body being capable of displacing according to external force;

a core made of magnetizable material connected to said displacing body;

an LC resonance circuit including a magnetic coil and said core being capable of moving close to and away from said magnetic coil according to the displacement of said displacing body;

spring means for supporting said core adjacent to said magnetic coil, said spring means being attached to said displacing body;

a clock unit of a microcomputer inputting continuous signals having a prescribed frequency to said LC resonance circuit;

a rectifying circuit connected to said LC resonance circuit, said rectifying circuit consisting of a diode and capacitor for smoothing the continuous signals from said LC resonance circuit;

a detecting circuit connected to terminals of said capacitor of said rectifying circuit, said detecting circuit including said microcomputer for detecting an amount of displacement of said displacing body on the basis of DC voltage from said rectifying circuit, said detecting circuit including an A/D converter for converting the DC voltage from said rectifying circuit into a digital value; and

a memory unit storing first and second data tables, said memory unit being connected to said computer, said memory unit being at least one of part of said computer and external to said computer, said first data table including parameters for converting the digital value into the amount of displacement of the displacing body, said second data table including parameters for converting the amount of displacement into an output measurement value.

2. The displacement sensor according to claim 1,

wherein resonance frequency of said LC resonance circuit is designed to change, with the movement of said core, in a range equal to or greater than said prescribed frequency.

3. The displacement sensor according to claim 1,

wherein said external force is fluid pressure, and

wherein said detecting circuit detects the fluid pressure on the basis of the amount of displacing of said displacing body.

4. The displacement sensor according to claim 3,

wherein said displacing body is a diaphragm capable of displacing according to the change of the fluid pressure, and

wherein said detecting circuit detects the fluid pressure on the basis of the amount of displacing of said diaphragm.

5. The displacement sensor according to claim 1,

wherein said external force is weight of an object member, and

wherein said detecting circuit detects the weight on the basis of the amount of displacing of said displacing body.

6. A displacement sensor comprising:

LC resonance circuits including a plurality of magnetic coils, and a core being made of a magnetizable material and capable of moving close to and away from said magnetic coils according to external force, said core is movably held by at least one spring, said plurality of magnetic coils being arranged in a substantially perpendicular manner relative to each other;

an oscillator for inputting continuous signals having a prescribed frequency to said LC resonance circuits;

rectifying circuits connected to said LC resonance circuits, each rectifying circuit consisting of a diode and a capacitor smoothing the continuous signals from said LC resonance circuits; and

detecting circuits connected to said rectifying circuits for detecting an amount of displacement of said core on the basis of DC voltage from each rectifying circuit, whereby acceleration of the movement of said core is calculated by each detecting circuit according to said displacement.