A metal detector has a transformer unit (1), a transmitter unit (2), a receiver coil set (3), a signal processing unit (4) and a control unit (5). The transformer unit provides an input signal (s.sub.IN) with selectable operating frequency (f.sub.TX) to an amplifier stage (12), that is connected to a transmitter coil (21) that is coupled to first and second receiver coils (31, 32). The coil outputs are connected to the signal processing unit, which has a receiver unit (41) and a signal processor (42). A coupling transformer (13) has first and second windings (13A, 13B), connected to the output of the amplifier stage, and a third winding (13C), connected to the transmitter coil. The first and second windings are each connected at a first end to a supply voltage (+Ub). Each of the first and second windings has at least one tapping (141, 142, 143, 144; 141, 142, 143, 144) at a same turn number counted from the first end. The amplifier stage has first and second amplification wings (12A, 12B). Each of these is associated with a power transistor connected to one of the at least one tappings of the corresponding winding, so the first and second amplification wings amplify the corresponding first and second half waves of the input signal.

An intruding metal detection method for a supplying-end module of an induction type power supply system having a supplying-end coil includes interrupting at least one driving signal of the induction type power supply system to stop driving the supplying-end coil during a measurement period, to generate a coil signal of the supplying-end coil; measuring a plurality of peaks of the coil signal within a plurality of consecutive oscillation cycles of the coil signal, to obtain a plurality of peak trigger voltages, respectively; calculating a first attenuation parameter according to a first peak trigger voltage and a second peak trigger voltage among the plurality of peak trigger voltages; and comparing the first attenuation parameter with a first threshold value to determine whether there is an intruding metal existing in a power supply range of the induction type power supply system.

A sensor apparatus for detecting a target object is provided, together with a corresponding method for operating the sensor apparatus. The sensor apparatus comprises a transmitter device which is operated by periodic excitation signals at a basic frequency, a receiver device which couples to the transmitter device, wherein the coupling is dependent on a relative position of the target object with respect to the receiver device, and the receiver device delivers signals at the basic frequency which are dependent on the relative position of the target object with respect to the receiver device. A threshold value checking device checks whether signals lie within or outside a threshold value range. A linking device acts on signals from the receiver device or signals derived therefrom in such a way that signals or signal combinations are shifted into the threshold value range insofar as they previously lay outside this range.

A multi-frequency platform for metal detection is disclosed. The transmission frequencies may be selected by the user or in an autonomous fashion. Further, the weighting of the frequencies may also be selected, either by the user or in an autonomous fashion. The ability to select transmission frequencies and weighting of the frequencies provides expanded detection capability, both in terms of the types of targets being sought and the types of ground conditions being experienced.

Various embodiments include apparatus and methods related to finding a position in an underground formation. Apparatus and methods can include receiving signals from a receiver in an underground formation in response to signals generated from transmitting sources, each of the transmitting sources located at a known position; and processing the received signals, based on the signals generated from the transmitting sources, to determine the position of the receiver. A number of techniques can be applied to processing the received signal. Additional apparatus, systems, and methods are disclosed.

Methods for operating a metal detector that includes a balanced coil system with a transmitter coil connected to a transmitter unit and first and second receiver coils connected to an input of a receiver unit. The transmitter unit includes a transmitter signal path for which a transmitter signal with at least one fixed or selectable operating frequency and a related quadrature signal are provided. The transmitter signal is applied to an input of a transmitter amplifier that forwards the amplified transmitter signal directly or via a transmitter matching unit to the transmitter coil. The receiver unit includes at least one receiver signal path in which the modulated receiver signal received from the balanced coil system is applied directly or via a receiver matching unit to a receiver amplifier, which applies the amplified modulated receiver signal directly or indirectly to a receiver phase sensitive detector, which compares the modulated receiver signal with reference signals, which correspond to the transmitter signal and the quadrature signal, to produce a demodulated complex receiver signal with in-phase receiver signal components and quadrature receiver signal components, which are processed in a signal processing unit which comprises at least one signal processing path, in which signal components of the complex receiver signal that relate to goods or noise are suppressed and in which signal components originating from metal contaminants are further processed. At least one transmitter measurement channel is provided, which receives a measurement signal taken from the transmitter signal path and which includes a measurement amplifier, which amplifies and forwards the measurement signal directly or indirectly to a measurement phase sensitive detector, which compares the measurement signal with the reference signals, which correspond to the transmitter signal and the quadrature signal, to produce a complex measurement signal with in-phase measurement signal components and quadrature measurement components, which complex measurement signal and complex receiver signal are applied to a first correction module in which signal components caused by instabilities of the transmitter unit are removed from the complex receiver signal.

Methods for operating a metal detector with a balanced coil system with a transmitter coil connected to a transmitter unit and a first and a second receiver coil connected to an input of a receiver unit, connected to a signal processing unit are provided. The transmitter unit includes a transmitter signal path for a transmitter signal with at least one fixed or selectable operating frequency. The transmitter signal is applied to an input of a transmitter amplifier that forwards the amplified transmitter signal directly or via a transmitter matching unit to the transmitter coil. The receiver unit includes at least one receiver signal path in which the receiver signal received from the balanced coil system is applied directly or via a receiver matching unit to a receiver amplifier, which forwards the amplified receiver signal directly or indirectly to a receiver demodulator that is provided in the receiver unit or is implemented in the signal processing unit. The receiver demodulator provides a demodulated complex receiver signal with in-phase receiver signal components and quadrature receiver signal components, which in-phase receiver signal components and quadrature receiver signal components are processed in least one signal processing path provided in the signal processing unit, in which signal components of the complex receiver signal that relate to products or noise are suppressed and in which signal components originating from metal contaminants are further processed. At least one measurement signal taken from the receiver signal path is provided to a measurement channel and analyzed in an evaluation module or in a receiver control module to provide related measurement information. Based on the obtained measurement information, the receiver control module determines if a critical condition, in which signal processing in the receiver signal path is possibly impaired, is present. A procedure for handling critical conditions in the metal detector is executed if a critical condition is present.

A dual detector includes a detection head having a platform and an inductive sensor that is mounted on the platform and includes a transmitter coil and a separate receiver coil. The transmitter coil and the receiver coil each form a loop, the loop of the transmitter coil at least partially overlapping the loop of the receiver coil so as to form a coupling region that is elongate in a first longitudinal direction defining a first axis, the arm extending on a plane that runs perpendicularly to the platform, and the first axis of the coupling region running transversely to the plane.

A metal detection system includes a detection module, a control module, a positioning module, and a computer module. The detection module includes an electromagnetic wave emitter that emits electromagnetic waves, and an electromagnetic wave receiver that senses electromagnetic signals emitted by underground metal in response to the electromagnetic waves emitted by the electromagnetic wave emitter. The control module processes the electromagnetic signals received by the electromagnetic wave receiver and generates metal detection data based on the received electromagnetic signals, or processes output signals provided by the detection module and generates metal detection data based on the output signals provided by the detection module. The positioning module generates information about positions of the metal detection device over time. The computer module performs: based on the information about positions of the metal detection device generated by the positioning module, showing locations that the metal detection device has traveled on a map; and based on the metal detection data, overlaying information indicating whether metal was detected at the locations traveled by the metal detection device on the map.

A portable terminal charging device includes a large diameter detection coil arranged between a charging coil and a portable terminal, and a further detection coil arranged inward of the large diameter detection coil and having a smaller diameter than the large diameter detection coil. The large diameter detection coil and the further detection coil detect a state of a foreign metal object by finding out a decrease in the magnetic flux of an inward section of the charging coil and conversely finding out an increase in the magnetic flux of an outward section thereof, if the foreign metal object is present between a portable terminal installation unit of a support plate and the portable terminal.