Patent ID: 7868758

Claim:
A passenger screening system, comprising: a floor having a top surface; an inductive sensor positioned under the top surface of the floor, the inductive sensor comprising: a first gradiometer configured to generate a first pair of opposing current paths and a second pair of opposing current paths substantially perpendicular to the first pair of current paths; and a second gradiometer disposed adjacent said first gradiometer and configured to generate a third pair of opposing current paths and a fourth pair of opposing current paths substantially perpendicular to the third pair of current paths, said first and second gradiometers each configured to operate at a first frequency associated with a first target substance and at a second frequency associated with a second target substance to facilitate detecting a presence of at least one of the first target substance and the second target substance wherein the first and second pairs of current paths cooperate to generate four distinct combinations of magnetic fields for detection of the presence of said at least one the first and second target substances.