Magnetic Field Response Sensor For Conductive Media

• US 20070013371A1
• Filed: 06/02/2006
• Published: 01/18/2007
• Est. Priority Date: 05/01/2003
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: U.S.A. as represented by the Administrator of the National Aeronautics and Space Administration
• Inventors: Taylor, Bryant, Woodard, Stanley
• Granted Patent: US 7,589,525 B2
• Time in Patent Office: Days
• US Class Current: 324/239
• CPC Class Codes: G01L 1/14 by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators

Abstract

A magnetic field response sensor comprises an inductor placed at a fixed separation distance from a conductive surface to address the low RF transmissivity of conductive surfaces. The minimum distance for separation is determined by the sensor response. The inductor should be separated from the conductive surface so that the response amplitude exceeds noise level by a recommended 10 dB. An embodiment for closed cavity measurements comprises a capacitor internal to said cavity and an inductor mounted external to the cavity and at a fixed distance from the cavity'"'"'s wall. An additional embodiment includes a closed cavity configuration wherein multiple sensors and corresponding antenna are positioned inside the cavity, with the antenna and inductors maintained at a fixed distance from the cavity'"'"'s wall.

Claims

1. A magnetic field response sensor for acquiring physical state measurements of a conductive material, comprising:

an inductive element positioned at a fixed separation distance from a surface of said conductive material; and

a capacitive element in operative communication with said inductive element and affixed to said conductive surface.

2. The sensor of claim 1, wherein said fixed separation distance is maintained by a nonconductive layer disposed between said inductive layer and said conductive surface.

3. The sensor of claim 1, wherein said inductive element is separated from said conductive surface such that said inductive element'"'"'s response amplitude exceeds noise level by about 10 dB.

4. The sensor of claim 1, wherein said fixed separation distance is at least about 0.375 inches.

5. The sensor of claim 1, wherein said inductive element is positioned at a fixed angle from said conductive surface.

6. The sensor of claim 1, further comprising means for effecting movement of said inductive element from a first position to a second position.

7. A magnetic field response sensor for closed cavity measurements, comprising:

an inductive element positioned at a fixed separation distance external to said closed cavity; and

a capacitive element in operative communication with said inductor and positioned internal to said cavity.

8. A magnetic field response measurement system for closed cavity measurements, comprising:

a plurality of sensors internal to said cavity;

an antenna internal to said cavity and separated from said cavity'"'"'s wall for supplying a magnetic field, thereby creating an electrical current in said sensors via Faraday induction, further wherein said sensors'"'"' inductors are maintained at a fixed position relative to and separated from said cavity'"'"'s wall.