A magnetic field sensing apparatus including a magnetic flux concentrator and a plurality of magnetoresistance units is provided. The magnetic flux concentrator has a top surface, a bottom surface opposite to the top surface, and a plurality of side surfaces connecting the top surface and the bottom surface. The magnetoresistance units are respectively disposed beside the side surfaces. The magnetoresistance units are electrically connected to form at least one kind of Wheatstone full bridge in three different periods, so as to measure magnetic field components in three different directions, respectively, and to cause the at least one kind of Wheatstone full bridge to output three signals corresponding to the magnetic field components in the three different directions, respectively.

A metal detection apparatus includes a detector housing with input and output apertures delimiting a transfer channel for moving products through a coil system with a transmitter coil for inducing signals in receiver coils that do not compensate one another when a metal contaminant is in the detection zone. A test device includes at least one sample, a signal processing unit for processing the receiver coil signals and detecting signals relating to contaminants and the test sample, and a control unit for controlling measurement of products during normal operation and the sample during test intervals. The test device includes reel units at the input and output apertures, respectively, with drive units rotatably holding reels holding ends of an elongated windable sample carrier extending through the detection zone and holding the sample(s). Either or both of the reel drive units transfer the sample(s) through the detection zone during test intervals.

A system and method of object detection using a multi-property array-based object detection system. A hybrid multi-sensor gateway (MSG) system combines transmitters and receivers into a single gateway. The hybrid system consists of the backbone of a multi-sensor gateway system with an active transmitter loop which induces eddy currents to flow within conductive targets. Acquisition parameters such as transmitter pulse base frequency, waveform shape, ramp-time and peak current can be modified and tuned to the specific applications and expected targets.

A bobbin and coil architecture is provided for use in an inductive sensor. The architecture eliminates the need for coil shielding and reduces the sensor's sensitivity to temperature and proximate mounting hardware. In one or more embodiments, all or portions of separate coils are located in a common slot on the bobbin, rather than being segregated into separate slots. In an example configuration, two receiver coils may be located in respective two slots on the bobbin, and a transmitter coil may divided into two substantially equal subsets of windings, with each subset wound together with one of the receiver coils in a common slot. This yields a symmetrical and balanced winding architecture that requires fewer slots relative to designs that segregate all coils into separate slots.

A magnetic field sensing system may include a first magnetic field sensing element; a second magnetic field sensing element; means for generating a first magnetic field having a first non-zero frequency; means for generating a second magnetic field having a second frequency; a conductive target positioned to generate a reflected magnetic field in response to the first magnetic field; means for producing a first signal representing the first magnetic field and the reflected magnetic field during a first alternating time period; means for producing a second signal representing the second magnetic field during a second alternating time period; means for calculating an error value as a function of the first and second signals, wherein the error value is based, at least in part, on the second signal during the first time period; and means for applying the error value to the first signal during the first alternating time period.

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 bucking system for an electromagnetic survey system which uses a network to interconnect the turns of a transmitter coil with the turns of one or more bucking coils in which the network includes passive circuit elements which to provide accurate bucking of the transmitter coil field at a sensor location, both when the current through the loop is steady and when the current is changing rapidly.

A self-balance noise reduction metal detection double-coil comprises a main magnetic field transmitting coil and a plurality of induction coils. Each induction coil is composed of two inductors and induction unicoils in series connection, wherein the induction unicoils have similar Q values and are arranged in parallel. Every two adjacent induction coils are arranged in an overlapping mode. The multiple induction coils are arranged in the main magnetic field transmitting coil. The induction coils do not need to be adjusted, and the self-balance noise reduction metal detection double-coil is high in anti-electromagnetic interference capacity, unlikely to cause false alarms and free of weak induction zones, can normally operate in complex metal environments without being distributed, and is simple in structure, easy to machine and suitable for volume production.