Magnetic field response sensor for conductive media

• US 7,589,525 B2
• Filed: 06/02/2006
• Issued: 09/15/2009
• 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: The United States Of America As Represented By The National Aeronautics And Space Administration
• Inventors: Taylor, Bryant D., Woodard, Stanley E.
• Primary Examiner(s): LeDynh; Bot L
• Application Number:
  US11/421,886
• Publication Number:
  US 20070013371A1
• Time in Patent Office: 1,201 Days
• Field of Search: 324/239, 324/244, 324/260, 324/207.11, 324/207.15, 235/439, 235/449, 235/451, 737/18, 737/24
• 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 within a cavity enclosed by electrically conductive walls, comprising:

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

a capacitive element in operative communication with said inductive element and affixed to an inner surface of said conductive walls, wherein said inductive element is separated from said outer surface such that said inductive element'"'"'s response amplitude exceeds noise level by about 10 dB.

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

an inductive element positioned external to said closed cavity and at a fixed separation distance with respect thereto such that said inductive element'"'"'s response amplitude exceeds noise level by about 10 dB; and

a capacitive element in operative communication with said inductive element and positioned internal to said closed cavity, wherein said closed cavity is enclosed by electrically conductive walls.

3. The sensor of claim 2, wherein said fixed separation distance is maintained by a nonconductive layer disposed between said inductive element and said closed cavity.

4. The sensor of claim 2, wherein said fixed separation distance is at least about 0.375 inches.

5. The sensor of claim 2, wherein said inductive element is positioned at a fixed angle from said closed cavity.

6. The sensor of claim 2, further comprising means for effecting movement of said inductive element from a first position to a second position.