Eddy current sensor for non-destructive testing the quality of electrically conductive through-hole plating in printed circuit boards

An eddy current sensor for non-destructive testing of quality of electrically conductive through-hole plating in printed circuit boards having termination pads comprising:

• an elongated magnetic probe member with a first end and a second end movable into a hole of said printed circuit board when the latter is positioned in the path of movement;
• means for moving said magnetic probe member for inserting said magnetic probe member into said hole of said printed circuit board;
• a first winding coaxial with said magnetic probe member for inducing eddy currents in electrically conductive through-hole plating of printed circuit boards when the latter are positioned adjacent thereto;
• a second winding coaxial with the probe's path of movement and magnetically coupled with and rigidly fixed with respect to said first winding and positioned at a predetermined distance from said first winding for forming a gap for said test printed circuit board to be inserted;
• a plurality of coaxial coplanar sections of said second winding in aiding connection between each other and positioned at a predetermined radial distance from said magnetic probe member symmetrically to its axis, said sections projecting radially within limits of corresponding termination pads of said through-plated hole in said test printed circuit board;
• a third winding coaxial with the probe's path of movement and connected in opposition to said second winding and magnetically coupled with said first winding, said third winding being rigidly fixed with respect to said first winding and said second winding and being positioned at a predetermined distance from said first winding on the other side in relation to said second winding with a gap provided for insertion of an additional printed circuit board;
• said third winding having a plurality of coaxial coplanar sections in aiding connection and positioned at a predetermined radial distance from said magnetic probe member symmetrically about its axis, said sections of said third winding projecting radially within limits of respective termination pads of said through-plated holes of the additional printed circuit board, said first winding comprising an exciting winding, said second and third windings comprising measuring windings located on opposite sides of said first winding, said measuring windings being rigidly fixed relative to said exciting winding and said probe, when moved, being positioned within said windings and said through holes.