A tri-axis magnetometer comprising three giant-magnetoresistance sensors and a cylindrical fluxguide are implemented for compass application. The sensors are mounted on a single printed circuit board (PCB) board with their sensing axes in a plane. A calibration process involving matrix manipulation was employed to make the device function as a tri-axis magnetometer with orthogonal sensing directions. The capability of the device for compass application was demonstrated by measuring its azimuth response to the geomagnetic field about different rotation axes. The proposed calibration technique can be used for the magnetometer system with either orthogonal or non-orthogonal sensor arrangement.

Intracranial hemorrhage (ICH) resulting from traumatic brain injury is a serious issue, often leading to death or long-term disability if not promptly diagnosed. Currently, doctors primarily use Computerized Tomography (CT) scans to detect and precisely locate a hemorrhage, typically interpreted by radiologists. However, this diagnostic process heavily relies on the expertise of medical professionals. To address potential errors, computer-aided diagnosis systems have been developed. In this study, we propose a new method that enhances the localization and segmentation of ICH lesions in CT scans by using multiple images created through different data augmentation techniques. We integrate residual connections into a U-Net-based segmentation network to improve the training efficiency. Our experiments, based on 82 CT scans from traumatic brain injury patients, validate the effectiveness of our approach, achieving an IOU score of 0.807 ± 0.03 for ICH segmentation using 10-fold cross-validation.

The high sensitivity for low-frequency fields makes the tiny giant magnetoresistance (GMR) sensors suitable for high-resolution eddy-current (EC) imaging. In this work, we proposed a novel design of the miniature differential EC probe with a spin-valve GMR sensor for surface and subsurface EC imaging. The differential EC probe consists of a full-bridge GMR chip mounted vertically on the edge of a tiny printed circuit board to reduce the liftoff distance. The excitation signal is perpendicular to the sensing axis of the GMR chip, which makes it sensitive to the unbalance EC signal on the surface of a conductive sample. The miniature EC probe operated at frequencies from 5 to 65 kHz is sensitive to the hidden defects on a flat conductor. The spatial resolution and stability of the device are verified by taking the 2-D scan images over the copper film samples with hidden defects, showing that the spatial resolution is better than 2 mm for the flaw 0.5 mm below the top surface of a multilayer structure. The proposed device is useful in the detection of small surface and subsurface defects, such as cracks, metal loss, and other mechanical damages.

This work presents a flaw detection system consisting of an array of eddy current (EC) probes based on giant-magnetoresistance (GMR) sensors for mapping the defects on a metal sheet. Before measurement, a spatially dependent calibration process was done to compensate for the interchannel inconsistency in output offsets and responsivity. The calibrated eight-channel probe array exhibits high sensitivity in revealing tiny features of defects with superior spatial resolution. The proposed system allows for the visualization of the geometric characteristics of the surface defects with an interspacing of more than 2 mm. The suggested approach has great potential in the nondestructive testing of metallic sheets for the characterization of minor and intricately shaped flaws.

A miniature tri-axis magnetometer with in-plant giant magnetoresistance (GMR) sensors and a fluxguide was designed, implemented and characterized in this work. Three GMR sensor dies were aligned on a printed circuit board (PCB) with their sensing directions in the same plane. By using the flux bending effect of a fluxguide, the magnetic field components in the mounting plane of GMR sensors were generated and hence the effective sensing directions are not in the same plane. The tilt of effective sensing direction from the mounting plane allows the device to detect the out-of-plane field component. When the device was used as an electronic compass, the digitally demodulated sensor outputs were converted into the orthogonal geomagnetic field components by using a real-time conversion process with the voltage-to-field transfer matrix. The result shows that the device is suitable for compass application. Further works to implement the similar design on a CMOS chip with integrated GMR elements and a planar modulation coil will realize a compact and easy-to-fabricate tri-axis magnetic field sensor.

Responsivity and field noise of a bridge-type GMR magnetometer modulated by a sinusoidal alternating magnetic field were investigated in this work. The odd harmonics of output voltage were found to be more sensitive to external dc fields in comparison with the even harmonics. By detecting the field-modulated output with a reference square wave at the 1st, 3rd, or 5th harmonic of modulation frequency, the sensor responses to external fields are bipolar, non-hysteretic, and quite linear with proper modulation amplitudes. The minimum field noises were 5, 2.5, and 5 nT/√Hz at 1 Hz for the 1st, 3rd, and 5th harmonics, respectively, with power consumption less than 10 mW. The proposed operation method is promising for application to electronic compasses.