Simultaneous time-domain and frequency-domain metal detector
First Claim
1. A metal detector configured to operate in both a time-domain mode and a frequency-domain mode, the metal detector comprising:
- a transmitter comprised of;
a transmitter coil;
a generator for generating an oscillatory wave current signal to be applied to the transmitter coil for operating in the frequency-domain mode;
a direct current source for generating a current signal to be applied to the transmitter coil for operating in the time-domain mode;
means for combining the oscillatory wave current and direct current signals into a single composite transmitter current signal; and
a transmitter coil switch for switching the single transmitter current signal on and off to the transmitter coil, anda receiver comprised of;
a magnetic field detector for sensing eddy currents in nearby metal targets;
first receiver components configured to operate in the time-domain mode to detect metal targets; and
second receiver components configured to operate in the frequency-domain mode to detect metal targets,wherein the metal detector operates in(i) the frequency-domain mode while the transmitter coil switch is on to charge the transmitter coil with the direct current signal, and(ii) the time-domain mode while the transmitter coil switch is switched off.
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Accused Products
Abstract
A metal detector capable of operating in both a time-domain mode and a frequency-domain mode includes a transmitter component and a receiver component. The transmitter component includes a transmitter coil that can receive both an AC and DC current source for frequency-and time-domain operation respectively. The AC signal is impressed on the DC signal such that while the transmitter coil is charging, frequency-domain sensing is occurring and when the transmitter coil is switched off, time-domain sensing is occurring. The receiver component uses a primary field bucking method to ensure that both time-and frequency-domain modes can operate with the receiver coil.
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Citations
7 Claims
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1. A metal detector configured to operate in both a time-domain mode and a frequency-domain mode, the metal detector comprising:
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a transmitter comprised of; a transmitter coil; a generator for generating an oscillatory wave current signal to be applied to the transmitter coil for operating in the frequency-domain mode; a direct current source for generating a current signal to be applied to the transmitter coil for operating in the time-domain mode; means for combining the oscillatory wave current and direct current signals into a single composite transmitter current signal; and a transmitter coil switch for switching the single transmitter current signal on and off to the transmitter coil, and a receiver comprised of; a magnetic field detector for sensing eddy currents in nearby metal targets; first receiver components configured to operate in the time-domain mode to detect metal targets; and second receiver components configured to operate in the frequency-domain mode to detect metal targets, wherein the metal detector operates in (i) the frequency-domain mode while the transmitter coil switch is on to charge the transmitter coil with the direct current signal, and (ii) the time-domain mode while the transmitter coil switch is switched off. - View Dependent Claims (2, 3, 4, 5)
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6. A method of operating a metal detector including a transmitter coil for inducing a detectable magnetic field indicative of a nearby metal target, comprising:
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during a first time period (a) applying to the transmitter coil a composite current signal including an oscillatory current signal and a DC current signal;
concurrently(b) performing frequency domain metal detection based on a first magnetic field induced as a result of step (a); and during a second time period following the first time period (c) removing the composite current signal from the transmitter coil; and
then(d) performing time domain metal detection based on a second magnetic field induced as a result of step (c). - View Dependent Claims (7)
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Specification