Patent ID: 9348053
Filing Date: 2016-05-24
CPC Classification: G01V

Claim Text:
1. A method for detecting an electrically conducting target in soil, including the steps of: generating a repeating transmit signal cycle of a fundamental period using transmit electronics, the repeating transmit signal cycle including a first period and a second period within each fundamental period, wherein the first period is a transmit period with finite non-zero current flowing through the magnetic field transmitter; generating a transmit magnetic field using a magnetic field transmitter, based on the repeating transmit signal cycle, for transmission into the soil; receiving a receive magnetic field using a magnetic field receiver; producing a receive signal induced by the receive magnetic field; arranging for a current flowing through the magnetic field transmitter to flow to a first potential through a damping resistor during the second period for providing a damping effect on the current flowing through the magnetic field transmitter; arranging for the current flowing through the magnetic field transmitter to flow to a second potential, predominantly through an alternative path with a lower resistance than that of the damping resistor, during the first period, in order to short the receive signal to the second potential and to short the receive signal away from both the damping resistor and a preamplifier of receive electronics of the metal detector; monitoring the current flowing through the magnetic field transmitter to provide a control signal, the control signal, in effect, causing the second period to begin when the current flowing through the magnetic field transmitter is substantially zero; and processing the receive signal during at least part of the repeating transmit signal cycle to produce an indicator signal indicating the presence of an electrically conducting target when the target is within the influence of the transmit magnetic field.