Vector Magnetometer

矢量磁力仪

Detection technology utilizing local magnetic anomalies of ferromagnetic objects has be come an important trend in target detection. Detection of a magnetic dipole target usually includes determinations of its position and magnetic moment, which contains six scalar unknowns. Localization and magnetic moment estimation is conventionally realized by measuring the total magnetic intensity or magnetic field vectors, using magnetometers installed on a mobile platform. Vector magnetometers are largely used in practices, which measure the three components of the anomaly magnetic field. Either the three components, or the total field (the modulus value of the three components), or the tensor gradients, or a combination of them can be used to construct an optimization algorithm for inversion of the six quantities. We have explored TMR (Tunneling Magneto-resistive) and ME (Magnetoelectric) sensors as a viable one in extremely sensitive vector magnetometer and gradiometer.

Magnetic Anomaly Detection

磁异常探测

As a result of magnetization by the Earth’s magnetic field, a metallic material can create distortions in the local geomagnetic field along each of its three orthogonal directions. Magnetic anomaly detection (MAD) is the use of such phenomenon by magnetic sensors because of the passage of a metallic material nearby a stationary sensor or when a sensor is mounted on a moving platform to sense a stationary target. The MAD method has been proven to work aboard in traffic surveillance, vehicle parking , sea mine hunting, security checking, unexploded ordnance discrimination, subsea cable and underwater vehicle detection .

Electromagnetic Non-Destructive Test

电磁无损探伤

Eddy current (EC) testing is one of the most known and widely used non-destructive test (NDT) methods of conducting materials. EC testing represents a non-destructive electromagnetic inspection technology capable of both surface and subsurface flaws detection and sizing of conductive metals. Similar to the EC technique, the ACFM (alternating current field measurement) method relies on current-carrying wires to introduce a thin-skin eddy current in the work-piece. The ACFM technique employs a bi-axial magnetic sensor to gauge the magnetic field perturbation caused by a crack that can be used in a non-contact manner with no threat to operators. Also, the ACFM method does not require coating removal because it is relatively immune to the lift-off effect, clearly demonstrating its merit as a very NDT approach.

Magnetic Communication

磁通信

Magnetic communication is also called magnetic induction communication which is being widely used for near-field communication (NFC), such as underground and underwater communication. The classical electromagnetic waves do not work well in these harsh environments, and the acoustic communication underwater faces many problems, such as high propagation delays, very low data rates, and highly environment-dependent channel behavior. While the magnetic induction (MI) technique is a promising alternative wireless communication solution to deal with these situation. The MI technique utilizes the near magnetic field of coils to propagate the information, thus, achieving constant channel conditions via small size of coils. The negligible propagation delay, predictable constant channel response, sufficiently large communication range and high data rate make the MI communication suitable for NFC in harsh environments.

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