Non intrusive and dynamic method for measuring a distance or the variation thereof through dielectrics

• US 20040135588A1
• Filed: 02/11/2004
• Published: 07/15/2004
• Est. Priority Date: 03/23/2001
• Status: Active Grant

• Current Assignee: VibroSystM Inc. (Gestion Marius Cloutier, Inc.)
• Original Assignee: VibroSystM Inc. (Gestion Marius Cloutier, Inc.)
• Inventors: Pronovost, Jean, Cloutier, Marius, Bissonnette, Marc
• Granted Patent: US 7,064,559 B2
• Time in Patent Office: Days
• US Class Current: 324/662
• CPC Class Codes: G01B 7/023 for measuring distance between sensor and object G01B7/082 and G01B7/102 take precedence
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: G01H 11/00 Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties

Abstract

A non intrusive method and system for the dynamic measurement of a distance, or the variations over time thereof, constituting the thickness, or the variations thereof, of a thin compressible dielectric material located between one or several other closely spaced solid dielectric layers of constant thickness and a conductive or semi-conductive surface. This is achieved by positioning a capacitive sensor on the external layer of the dielectric material, the sensor being composed of two parallel plates electrically insulated from one another, feeding the first plate with a high frequency signal, measuring the voltage and current value over time generated by the high frequency signal between the plate of the sensor which is closest to the surface of the outer layer of dielectric material, and deducting the above distance or variations thereof.

Claims

1. A method for the non-contact measurement of the distance and of the variation over time thereof separating the surface of a grounded conductive or semi-conductive component from the nearest surface of one or several parallel layers of solid dielectric substances closely but variably spaced from said component and facing it, said variable distance being filled with a compressible dielectric substance, comprising the steps of:

positioning a capacitive sensor on the external surface of the external layer of said solid dielectric substances, said sensor being composed of a first and a second parallel superimposed conductive or semi-conductive plates electrically insulated from one another, and said plates being parallel to the parallel layers of dielectric substances;

feeding said first plate of said sensor a high frequency signal;

measuring the voltage and current values over time generated by said high frequency signal between the second plate of said sensor which is closest to the surface of said outer layer of solid dielectric substances and the facing surface of the conducting or semi-conducting component;

deducting by processing means, from the current values and variations, the values and variations over time of the distance separating the inner surface of the inner solid dielectric layer facing the surface of the conductive or semi-conductive component.

2. The method according to claim 1 wherein the compressible dielectric substance is air or gas and is situated anywhere between the parallel layers of solid dielectric substances.

3. The method according to claim 1 allowing the measurement of the permittivity and the variations over time thereof of a dielectric substance which thickness is constant and known and closely spaced with other closely spaced dielectric layers which respective permittivities and thickness are known.

4. The method according to claim 1 wherein the dielectric constants and thickness of each solid dielectric layers are known, thereby allowing not only to detect the variations of the distance over time but also the value of the distance itself at a given instant.

5. The method according to claim 2 allowing the measurement of the vibrations of the stator bars of an electric generator wherein the capacitive sensor is affixed on the rotor-side surface of the tightening wedge of the corresponding stator bar and wherein the distance to be measured over time is the air gap between the stator-side of said wedge and the rotor-side surface of said stator bar.

6. The method according to claim 2 allowing the measurement of the radial movements and vibrations of a shaft made of conductive or semi-conductive material and rotating in an heterogeneous and turbulent atmosphere charged with particles wherein a protective cover constituted of semi-rigid dielectric material creates a clean and variable air-gap between the capacitive sensor and the outer surface of said shaft by brushing against said outer surface.

7. The method according to claim 3 allowing the detection of the passage or the measurement of the change of level of a fluid in front of a capacitive sensor, said passage or change of level occurring in a space located anywhere between solid layers of dielectrics and a conductive or semi-conductive surface.