Electricity: measuring and testing – Of geophysical surface or subsurface in situ – For small object detection or location
Reexamination Certificate
2006-12-12
2006-12-12
Aurora, Reena (Department: 2862)
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
For small object detection or location
C324S239000
Reexamination Certificate
active
07148692
ABSTRACT:
A metal detector for detecting objects that are composed of non-ferrous metals. The metal detector provides for a reduced rate of false positive responses to objects composed of ferrous metals. A preferred metal detector according to the invention includes a transmitter for transmitting a time-varying electromagnetic signal and a receiver for receiving a responsive time-varying electromagnetic signal produced by the metal object. The metal detector also includes an analyzer for determining the resistive and reactive components of the responsive signal as respective first and second functions of the spatial position of the detector. A module for determining and comparing rates of change of the first and second functions at one or more spatial positions is included. Preferably, when the rates of change are the first derivatives or slopes of the functions, and when these are of the same sign, a result indicating that the metal object is non-ferrous is provided by the module.A preferred method for identifying with an improved degree of reliability a non-ferrous metal object versus a ferrous object. The resistive and the reactive components of the responsive electromagnetic signal are determined as respective first and second functions of the spatial position of the detector, and the rates of change of the first and second functions at one or more spatial positions are compared. Preferably, if the rates of changes are the first derivatives or slopes of the functions, and these are of the same sign, a result that the object is non-ferrous is provided.
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Aurora Reena
Birdwell & Janke, LLP
White's Electronics, Inc.
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