A detection apparatus, comprising a first voltage divider resistor, a second voltage divider resistor, a detection coil, and a transmit coil, wherein the detection coil is a planar coil, and comprises 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 comprise at least one turn of continuously wound coil, and when the first group of coils, the second group of coils, or the third group of coils comprises a continuously wound multi-turn coil, the continuously wound multi-turn coil is coaxial; one end of the first voltage divider resistor is connected to one end of the first group of coils, the other end of the first voltage divider resistor is connected to one end of the second voltage divider resistor, and the other end of the second voltage divider resistor is connected to one end of the third group of coils; and when the detection apparatus is disposed in a first magnetic field, a voltage at two ends of the first voltage divider resistor is equal to a value of an induced electromotive force generated by the second group of coils in the first magnetic field, and a direction of the voltage at the two ends of the first voltage divider resistor is opposite to a direction of the induced electromotive force generated by the second group of coils in the first magnetic field; and the transmit 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. the detection coil is a planar coil, and comprises 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 comprise at least one turn of continuously wound coil, and when the first group of coils, the second group of coils, or the third group of coils comprises a continuously wound multi-turn coil, the continuously wound multi-turn coil is coaxial; one end of the first voltage divider resistor is connected to one end of the first group of coils, the other end of the first voltage divider resistor is connected to one end of the second voltage divider resistor, and the other end of the second voltage divider resistor is connected to one end of the third group of coils; and when the detection apparatus is disposed in a first magnetic field, a voltage at two ends of the first voltage divider resistor is equal to a value of an induced electromotive force generated by the second group of coils in the first magnetic field, and a direction of the voltage at the two ends of the first voltage divider resistor is opposite to a direction of the induced electromotive force generated by the second group of coils in the first magnetic field; and the transmit 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.