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Title: Method and apparatus for identifying conductive objects by monitoring the true resistive component of impedance change in a coil system caused by the object

The type of conductor, its property, and if a metal, its type and cross-sectional area can be obtained from measurements made at different frequencies for the amount of unbalance created in a previously balanced stable coil detection system. The true resistive component is accurately measured and thus reflects only the voltage loss attributable to eddy currents caused by introduction of the test sample to the coil system. This voltage divided by corresponding applied frequency gives a curve which peaks at a frequency dependent upon type of conductor. For a metal this peak frequency is proportional to the samples resistivity divided by its cross-sectional area.
Inventors:
 [1];  [2];  [3];  [4]
  1. (Vienna, VA)
  2. (McLean, VA)
  3. (Falls Church, VA)
  4. (Arlington, VA)
Issue Date:
OSTI Identifier:
863867
Assignee:
Georgetown University (Washington, DC) OSTI
Patent Number(s):
US 4263551
Contract Number:
AT(40-1)-3665
Research Org:
Georgetown Univ., Washington, D.C. (USA)
Country of Publication:
United States
Language:
English
Subject:
method; apparatus; identifying; conductive; monitoring; true; resistive; component; impedance; change; coil; caused; type; conductor; property; metal; cross-sectional; obtained; measurements; frequencies; amount; unbalance; created; previously; balanced; stable; detection; accurately; measured; reflects; voltage; loss; attributable; eddy; currents; introduction; sample; divided; corresponding; applied; frequency; curve; peaks; dependent; peak; proportional; samples; resistivity; eddy current; eddy currents; resistive component; accurately measure; accurately measured; impedance change; /324/