CONSTANT CURRENT METAL DETECTOR WITH DRIVEN TRANSMIT COIL
First Claim
Patent Images
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 one receive period and at least one non-zero transmit coil reactive voltage period;
b) a transmit coil having an inductance connected to the transmit electronics for receiving the repeating transmit signal cycle and generating a transmitted magnetic field;
c) a receive coil for receiving a received magnetic field during at least one receive period and providing a received signal induced by the received magnetic field;
d) at least one negative feedback loop for sensing a current in the transmit coil during at least one receive period to provide a control signal, the control signal controlling a magnitude and/or duration of the at least one non-zero transmit coil reactive voltage period such that the average value of the current during at least one receive period of every repeating transmit signal cycle is substantially constant, and the current during at least one receive period is substantially independent of the inductance of the transmit coil; and
e) receive electronics connected to the receive coil for processing the received signal during at least one receive period to produce an indicator output signal, the indicator output signal including a signal indicative of the presence of a metallic target in the soil.
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Accused Products
Abstract
A metal detector transmitting, through a transmit coil, a repeating transmit signal cycle, which includes at least one receive period and at least one non-zero transmit coil reactive voltage period; and sensing a current in the transmit coil during at least one receive period to control a magnitude and/or duration of the at least one non-zero transmit coil reactive voltage period such that the average value of the current during at least one receive period of every repeating transmit signal cycle is substantially constant, and the current during at least one receive period is substantially independent of the inductance of the transmit coil.
27 Citations
13 Claims
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1. A metal detector used for detecting a metallic target including:
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a) transmit electronics having a plurality of switches 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; b) a transmit coil having an inductance connected to the transmit electronics for receiving the repeating transmit signal cycle and generating a transmitted magnetic field; c) a receive coil for receiving a received magnetic field during at least one receive period and providing a received signal induced by the received magnetic field; d) at least one negative feedback loop for sensing a current in the transmit coil during at least one receive period to provide a control signal, the control signal controlling a magnitude and/or duration of the at least one non-zero transmit coil reactive voltage period such that the average value of the current during at least one receive period of every repeating transmit signal cycle is substantially constant, and the current during at least one receive period is substantially independent of the inductance of the transmit coil; and e) receive electronics connected to the receive coil for processing the received signal during at least one receive period to produce an indicator output signal, the indicator output signal including a signal indicative of the presence of a metallic target in the soil. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification