Transmit signal of a metal detector controlled by feedback loops

摘要

A metal detector has one or more feedback loops to control its repeating transmit signal cycle so that there is no reactive voltage drop across the transmit coil of the metal detector during at least one receive period of the metal detector.

主权项

1. A metal detector for detecting a metallic target in a soil including:
transmit electronics for generating a repeating transmit signal cycle, the repeating transmit signal cycle including at least one receive period and at least one non-zero transmit coil reactive voltage period; a transmit coil connected to the transmit electronics for receiving the repeating transmit signal cycle and generating a transmit magnetic field; a receive coil for receiving a receive magnetic field during the at least one receive period and providing a receive signal induced by the receive magnetic field; and receive electronics connected to the receive coil for processing the receive signal during the at least one receive period to produce an indicator output signal, the indicator output signal including a signal indicative of a presence of the metallic target when under an influence of the transmit magnetic field; wherein the repeating transmit signal cycle is generated such that a waveform of the repeating transmit signal cycle includes a substantially half-sine during the at least one non-zero transmit coil reactive voltage period, and that a current through the transmit coil is substantially constant and non-zero during the at least one receive period; the metal detector further including one or more feedback loops to control the repeating transmit signal cycle so that there is no reactive voltage drop across the transmit coil during the at least one receive period.