Eddy current detection

Abstract

Eddy current detection probes and related methods are disclosed. In some embodiments, the eddy current detection probes are hybrid probes, including a solid state sensor and a detection loop. In some embodiments, the eddy current detection probes include a drive coil and a detection loop, with the detection loop having a sensitive axis that is not parallel to principal axis of the drive coil. In some such embodiments, the sensitive axis of the detection loop is perpendicular to the principal axis of the drive coil.

What is claimed is: 
     
         1 . (canceled) 
     
     
         2 . An eddy current detection probe, comprising:
 a drive coil; and   a conductive detection loop oriented substantially perpendicular to the drive coil, wherein the conductive detection loop has a height that is substantially perpendicular to the drive coil and less than 2.5 mm.   
     
     
         3 . The eddy current detection probe of  claim 2 , wherein the drive coil is contained at least substantially within a plane, and wherein the plane is configured to be parallel to a surface of a material specimen probed by the eddy current detection probe. 
     
     
         4 . The eddy current detection probe of  claim 2 , wherein the conductive detection loop has a side disposed in a same plane as that in which the drive coil is disposed. 
     
     
         5 . The eddy current detection probe of  claim 2 , wherein the drive coil is configured to generate a drive magnetic field along a first axis, and wherein the conductive detection loop has a detection axis oriented substantially perpendicular to the first axis 
     
     
         6 . The eddy current detection probe of  claim 2 , further comprising:
 a substrate have a substantially planar surface;   wherein the drive coil is disposed on the substantially planar surface, and   wherein the conductive detection loop is wrapped at least partially around the substrate.   
     
     
         7 . The eddy current detection probe of  claim 2 , wherein the conductive detection loop is formed at least partially by a first electrical lead and a second electrical lead. 
     
     
         8 . The eddy current detection probe of  claim 2 , wherein the conductive detection loop encloses an area of less than approximately 0.2 square millimeters. 
     
     
         9 . The eddy current detection probe of  claim 2 , wherein the drive coil is formed on a printed circuit board. 
     
     
         10 . The eddy current detection probe of  claim 9 , wherein the conductive detection loop is formed at least partially on the printed circuit board. 
     
     
         11 . A method, comprising:
 exciting a drive coil of an eddy current detection probe with an alternating current (AC) signal having a frequency greater than approximately 1 MHz;   applying to a material under test an incident magnetic field generated by the drive coil as a result of exciting the drive coil; and   detecting an induced magnetic field from the material under test using a conductive detection loop oriented substantially perpendicular to the drive coil.   
     
     
         12 . The method of  claim 11 , wherein the conductive detection loop has a height that is substantially perpendicular to the drive coil and less than 1 mm. 
     
     
         13 . The method of  claim 11 , wherein the conductive detection loop has a height that is substantially perpendicular to the drive coil and less than 0.5 mm. 
     
     
         14 . The method of  claim 11 , wherein exciting the drive coil with an AC signal comprises exciting the drive coil with an AC signal having a frequency between approximately 2 MHz and 5 MHz. 
     
     
         15 . The method of  claim 11 , wherein exciting the drive coil with an AC signal comprises exciting the drive coil with an AC signal having a frequency greater than approximately 2 MHz. 
     
     
         16 . The method of  claim 11 , wherein applying to the material under test an incident magnetic field generated by the drive coil as a result of exciting the drive coil comprises orienting the drive coil substantially parallel to a surface of the material under test. 
     
     
         17 . The method of  claim 16 , wherein exciting the drive coil with an AC signal comprises exciting the drive coil with an AC signal having a frequency between approximately 2 MHz and 5 MHz. 
     
     
         18 . The method of  claim 17 , wherein the conductive detection loop has a height that is substantially perpendicular to the drive coil and less than 2.5 mm. 
     
     
         19 . The method of  claim 11 , wherein the detected signal is preconditioned by applying a bucking signal, comprising an inverted reference signal at the drive frequency. 
     
     
         20 . The method of  claim 19 , wherein the reference signal is obtained by making a reference measurement at a point of an article to be tested known to be free of defects. 
     
     
         21 . A method of manufacturing an eddy current detection probe, comprising:
 fabricating a conductive drive coil on a first layer of a multi-layered substrate;   fabricating conductive traces on at least two layers of the multi-layered substrate; and   interconnecting with conductive material the conductive traces on the at least two layers of the multi-layered substrate to form a detection loop substantially perpendicular to the conductive drive coil.