DETECTION DEVICE

A detection coil, a detection apparatus, and a detection system are used to resolve a prior-art problem that a metal foreign matter detection method has relatively low efficiency. In this application, the detection coil is a planar coil, and includes a first group of coils, a second group of coils, and a third group of coils that are continuously wound and coaxial, and the second group of coils is located between the first group of coils and the third group of coils. The first group of coils, the second group of coils, and the third group of coils each include one turn of coil or a continuously wound multi-turn coil, and the continuously wound multi-turn coil is coaxial. A sum of induced electromotive forces generated by the first group of coils and the third group of coils in a first magnetic field is equal to a value of an induced electromotive force generated by the second group of coils in the first magnetic field, and directions are opposite. A coil that generates the first magnetic field is coaxial with the first group of coils, the second group of coils, and the third group of coils. When a metal foreign matter exists, a sum of the induced electromotive forces of the first group of coils, the second group of coils, and the third group of coils is not zero.