Patent ID: 7924012

Claim:
An electronic metal detector having a transmit coil arranged and adapted to transmit an alternating magnetic field associated with a reactive transmit coil voltage, the transmit coil is connected to transmit electronics arranged and adapted to generate a transmit signal, the transmit electronics having at least two power sources, a first power source and a second power source, wherein the first power source being adapted and arranged to connect to the transmit coil for at least a first period, and the second power source being adapted and arranged to connect to the transmit coil for at least a second period, said transmit electronics comprising at least one servo control negative feedback loop, a first servo control negative feedback loop, which is adapted and arranged to monitor a transmit coil current for at least part of said first period, and to control at least part of said transmit signal, the transmit electronics being adapted and arranged to control the transmit signal to produce the reactive transmit coil voltage to be approximately constant and approximately equal to zero whilst the transmit coil current is non-zero and approximately constant for at least part of the first period, receive electronics adapted and arranged to receive and process a receive magnetic field during at least some of the first period to produce an indicator output.