A means to enable the inspection of industrial materials in order to see hidden structural defects that can lead to an early failure, using electromagnetic fields and harmonic waves.

For near field communications, inductive coils coupled to each communicating circuit are brought close together so that there is inductive coupling between the two coils. Data signals can then be relayed between the two circuits without any direct connection between them. However, the system is susceptible to common mode noise, such as ambient EMI. In addition to the active coil pairs used for transmitting and receiving data, a pair of passive coils is provided, proximate to the active coil pairs, that is only used for detecting the ambient EMI. The EMI signals detected by the passive coils are processed by a noise detector/processor, and the noise detector processor then controls the transmitters and/or receivers to at least partially compensate for the detected EMI signals. Transmit power or receiver thresholds may be controlled by the noise detector/processor to improve the signal-to-noise ratio, or other compensation techniques can be used.

A sensor for locating metal or magnetic objects includes a first and a second transmitting coil and one receiving coil. The receiving coil includes a first and a second receiving sub-coil. The first transmitting coil and the first receiving sub-coil are arranged in a first plane. The second transmitting coil and the second receiving sub-coil are arranged in a second plane. The first transmitting coil and the first receiving sub-coil are offset in relation to the second transmitting coil and the second receiving sub-coil with respect to a common center axis which passes vertically through the planes. The first receiving sub-coil is configured differently than the second receiving sub-coil.

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.

An antenna arrangement. The arrangement uses four conductive loops, each within a distinct plane from the other conductive loops. The four conductive loops have a common center point. Each loop is within a dipole magnetic field, and detects a component thereof. By balancing the signals received between matched pairs of the conductive loops, the difference between the signals can be used to guide the antenna arrangement to a null pointthat isa point in the magnetic field where each pair of conductive loops is balanced. The antenna arrangement can further be used to determine the depth of the dipole field source using the magnitude of the field.

The invention relates to an inductive proximity switch having a primary coil for generating an alternating magnetic field, with an oscillator for driving the primary coil, with a control and evaluation unit, which is operatively connected to the oscillator and is equipped to acquire and evaluate an amplitude and a phase position of a current in the primary coil and for outputting a detection signal depending on the acquired current in the primary coil, with at least one compensation coil for manipulation of the alternating magnetic field generated by the primary coil. The inductive proximity switch is characterized in that a separate controllable current source is present for controlling the at least one compensation coil.

A metal sensor, a method for analyzing a measurement signal of the sensor, and a method for detecting an object surrounded by a medium via the sensor. The metal sensor has at least one transmission coil and at least one receiving coil system inductively coupled to each other, wherein the receiving coil system comprises at least one first receiving coil and at least one second receiving coil located in a same plane; the transmission coil forms a projection on the plane; an area formed by the first receiving coil on the plane contains the projection; and an area formed by the second receiving coil on the plane is arranged around the projection. The receiving coils are arranged to have a same winding direction, produce induction with a second magnetic field generated by a target metal object, and generate induced voltages superimposed on one another other on the receiving coils.

In a first technique one or more tuned circuits (traps) are placed in series in the metal detector coil, tuned to the operating frequency of the other sensor. In another technique a single turn coil of wire, or a small number of turns coil, is used as the metal detector coil, in combination with a step up transformer at the coil feed, to increase the EMF of the coil. In a further technique, the metal detector coil is formed in a plane that has regard to the sensing field of the other sensor. In another technique, the feed for the metal detector coil comprises a twisted pair of wires, which are routed along an axis in order to try to minimize and equalize the effect of the metal detector feed on the operation of the other antenna.

A magnetic field sensing apparatus including a magnetic flux concentrator, a plurality of magnetoresistance units, and a plurality of magnetization direction setting elements 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 an unchangeable Wheatstone full bridge. The magnetization direction setting elements set the magnetization directions of the magnetoresistance units into three different combinations in three different periods, respectively, so as to enable the unchangeable Wheatstone full bridge to respectively measure the magnetic field components in the three different directions in the three different periods.

A sensor system for sensing the contents of a bore including a plurality of coils disposed behind a non-metallic lining. An oscillator circuit may be used to drive the coils to generate oscillating electromagnetic fields, and a detection circuit generates output signals from each coil representing a parameter of the electrical oscillations that depends on the contents of the bore. The coils may include a primary coil and a one secondary coil, wherein the oscillating electromagnetic field generated by the secondary coil has a lesser degree of interaction with the contents of bore than the oscillating electromagnetic field generated by the primary coil. The sensor system may use the output signal from the secondary coil to compensate the output signal from the primary coil for environmental effects.