Patent ID: 7893691

Claim:
An electromagnetic impedance sensor for detecting an object with contact-free, wherein the object is made of conducting material or soft magnetic material, the sensor comprising: a detection coil having a coil surface, which faces a detection area in which the object is disposed; and a detection circuit for supplying alternating electricity to the detection coil and for detecting the object by measuring change of an electromagnetic impedance in the detection coil, wherein the detection coil includes a plurality of coil portions, which are provided by one wire, each coil portion is disposed on the coil surface to have a predetermined arrangement, the plurality of coil portions is sequentially arranged along with a first direction and includes one coil portion adjacent to another coil portion, the one coil portion has a side, which is adjacent to a corresponding side of the another coil portion, the side of the one coil portion extends along with a second direction, and the corresponding side of the another coil portion extends along with the second direction, the first direction is different from and perpendicular to the second direction, the side of the one coil portion has a current flowing direction, which is the same as a current flowing direction of the corresponding side of the another coil portion, each coil portion includes a first side and a second side, the first side extends along with the first direction, and the second side extends along with the second direction, and wherein the plurality of coil portions includes first to sixth coil portions, the first to third coil portions are arranged along with the first direction, and the fourth to sixth coil portions are arranged along with the first direction, the first and fourth coil portions, the second and fifth coil portions and the third and sixth coil portions are arranged along with the second direction, respectively, and each coil portion provides an at least two-turn coil.