Patent ID: 7791345
Filing Date: 2010-09-07
Classification: G01V

Abstract:
1. A metal detector used for detecting a metallic target including: a) transmit electronics having a plurality of switches for generating a repeating transmit signal cycle, the repeating transmit signal cycle including at least a high voltage period, and at least a low voltage period, the low voltage period followed by a substantially zero voltage period, wherein an average voltage during the high voltage period and an average voltage during the low voltage period are opposite in polarity, and an average absolute voltage during the high voltage period is higher than an average absolute voltage during the low voltage period; b) a transmit coil connected to the transmit electronics for receiving the repeating transmit signal cycle and transmitting a magnetic field wherein during the low voltage period and the substantially zero voltage period, an output impedance of the transmit electronics is less than three times the equivalent series resistance of the transmit coil; c) a receive coil for receiving a received magnetic field during at least one low voltage period and providing a received signal induced by the received magnetic field; and d) receive electronics connected to the receive coil for processing during at least one low voltage period the received signal to produce an indicator output signal, the indicator output signal including a characteristic indicative of the presence of a metallic target within the transmit magnetic field.