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 . <EOS>