Time domain method and apparatus for metal detectors

摘要

This invention provides a pulse induction metal detector where a coil transmits a pulsed magnetic field to energize metal objects that are often buried or hidden in a matrix (ground) containing ferromagnetic minerals. A difficult challenge is to detect and identify the metal object while ignoring the ferromagnetic matrix. Techniques are presented for achieving this.

主权项

1. A metal detector comprising
(a) a transmit coil for producing a periodic transmitted magnetic field in response to an applied periodic transmit current, in which each period is comprised of one or more transmit current turn-on charge times, each of which is followed by a turn-off time in which no current is applied; (b) a transmit circuit for creating the transmit current comprising a high voltage source and a low voltage source, whereby the high voltage source is switched in during the turn-on charge time of the transmit coil to effect a substantially instantaneous transition to a desired current, then the low voltage source is switched in to maintain the desired current at a substantially steady-state value; (c) a receive circuit capable of sampling the received signal created from the transmitted magnetic field and its effect on a surrounding matrix and conductive targets, and processing the one or more samples.