Magnetic field response sensor for conductive media

• US 7,759,932 B2
• Filed: 07/31/2009
• Issued: 07/20/2010
• 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: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Woodard, Stanley E., Taylor, Bryant Douglas
• Primary Examiner(s): LeDynh; Bot L
• Application Number:
  US12/533,520
• Publication Number:
  US 20090315546A1
• Time in Patent Office: 354 Days
• Field of Search: 324/239, 324/244, 324/260, 235/439, 235/449, 235/451
• 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 measurement system for measurements within an electrically conductive cavity, 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 time-varying 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.

2. The system of claim 1, wherein said inductors are separated from said cavity'"'"'s wall such that each said sensor'"'"'s response amplitude exceeds noise level by about 10 dB.

3. The system of claim 1, wherein said fixed position of each of said inductors is separated from said cavity wall at a distance that will allow each sensor response amplitude to exceed noise level by 10 dB.