Magnetic Field Sensor Research Articles

Photonic crystal fiber sensors to excite surface plasmon resonance based on elliptical detection channels are used for highly sensitive magnetic sensing

To improve the detection performance of fiber optic magnetic field sensors a new photonic crystal fiber (PCF) based on surface plasmon resonance (SPR) was designed and investigated. The designed sensor uses an elliptical detection channel, and the modal transmission characteristics and magnetic field sensing characteristics of this fiber optic sensor are analyzed using the full vector finite element method (FVFEM). In addition, the effect of the detection channel on the detection accuracy at different curvatures was investigated. Compared with previous optical fiber magnetic field (MF) sensors, the designed sensor meets the requirements of both refractive index (RI) and MF measurements, and the MF sensitivity, RI sensitivity, and amplitude sensitivity (AS) of the sensor reach 0.739 nm/Oe, 12043.8 nm/RIU, and 754.88RIU−1, respectively. The designed sensor expands the application range of optical fiber sensors and reduces the cost. It has great potential for application in complex environments.

Fabrication and Characterization of Monolithic Integrated Three-Axis Acceleration/Pressure/Magnetic Field Sensors.

In order to realize the measurement of three-axis acceleration, pressure, and magnetic field, monolithic integrated three-axis acceleration/pressure/magnetic field sensors are proposed in this paper. The proposed sensors were constructed with an acceleration sensor consisting of four L-shaped double beams, two masses, middle double-beams, and twelve piezoresistors, a pressure sensor made of a square silicon membrane, and four piezoresistors, as well as a magnetic field sensor composed of five Hall elements. COMSOL software and TCAD-Atlas software were used to simulate characteristics of integrated sensors, and analyze the working principles of the sensors in measuring acceleration, pressure, and magnetic field. The integrated sensors were fabricated by using micro-electro-mechanical systems (MEMS) technology and packaged by using inner lead bonding technology. When applying a working voltage of 5 V at room temperature, it is possible for the proposed sensors to achieve the acceleration sensitivities of 3.58 mV/g, 2.68 mV/g, and 9.45 mV/g along the x-axis, y-axis, and z-axis (through an amplifying circuit), and the sensitivities towards pressure and magnetic field are 0.28 mV/kPa and 22.44 mV/T, respectively. It is shown that the proposed sensors can measure three-axis acceleration, pressure, and magnetic field.

Optimising the sensitivity of optically-pumped magnetometer magnetoencephalography to gamma band electrophysiological activity

Abstract The measurement of electrophysiology is of critical importance to our understanding of brain function. However, current non-invasive measurements—electroencephalography (EEG) and magnetoencephalography (MEG)—have limited sensitivity, particularly compared to invasive recordings. Optically-Pumped Magnetometers (OPMs) are a new type of magnetic field sensor which ostensibly promise MEG systems with higher sensitivity; however, the noise floor of current OPMs remains high compared to cryogenic instrumentation and this limits the achievable signal-to-noise ratio of OPM-MEG recordings. Here, we investigate how sensor array design affects sensitivity, and whether judicious sensor placement could compensate for the higher noise floor. Through theoretical analyses, simulations, and experiments, we use a beamformer framework to show that increasing the total signal measured by an OPM array—either by increasing the number of sensors and channels, or by optimising the placement of those sensors—affords a linearly proportional increase in signal-to-noise ratio (SNR) following beamformer reconstruction. Our experimental measurements confirm this finding, showing that by changing sensor locations in a 90-channel array, we could increase the SNR of visual gamma oscillations from 4.8 to 10.5. Using a 180-channel optimised OPM-array, we capture broadband gamma oscillations induced by a naturalistic visual paradigm, with an SNR of 3; a value that compares favourably to similar measures made using conventional MEG. Our findings show how an OPM-MEG array can be optimised to measure brain electrophysiology with the highest possible sensitivity. This is important for the design of future OPM-based instrumentation.

Modeling of an Integrated Traction Motor Protection System

Purpose. The article is devoted to the creation of traction motor protection by modern methods and means based on a programmable logic controller (PLC). Methodology. To simulate motor fault monitoring in laboratory conditions, magnetic field and temperature sensors were installed on a small powerful induction motor, and then the data obtained from the sensors in normal and overloaded motor modes were analyzed. Based on the research, protection methods were developed. Findings. Previously used simple motor protection systems based on components such as timers, contactors, electromagnetic switches, voltage and current transformers were slow and inaccurate, and had low sensitivity. However, the production of PLCs and their application in this industry has eliminated these problems. The intensive operation of motors as the main executive equipment requires the creation of modern automated protection systems to ensure their reliable and stable operation. Originality. The paper improves the method of protection of traction motors based on the use of programmable logic controllers. In addition to the voltage and current parameters, the proposed method involves monitoring the magnetic field. It also provides for the possibility of adjusting the protection response time. As a result, in the event of overload, short circuit, and other non-standard situations, the improved method provides the system with the ability to make more accurate and reliable decisions. Practical value. The TIA Portal software package has modeled a traction motor protection system by temperature and current and considered its practical application. To make such systems more effective, in the future, comprehensive protection systems based on the diagnostic state of the traction motor can be developed. In addition, an effective system can be created by providing SCADA control of the engines of several vehicles simultaneously.

MEMS miniaturized low-noise magnetic field sensor for the observation of sub-millihertz magnetic fluctuations in space exploration

The objective of this paper is to show that, using magnetic field modulation with a MEMS resonator, it is possible to reduce the noise floor of a commercial Tunneling Magnetic Resistance by one order of magnitude, in the ultra-low frequency range. Low noise at this frequency range is a strong requirement in planetary or space exploration missions like LISA (Laser Interferometer Space Antenna), where the observed gravitational waves will be in the 0.1 mHz to 0.1 Hz range. It will be shown that the noise spectral amplitude after demodulation from 0.1 mHz to 100 mHz is well below the 100 nT/Hz requirement for the future space-borne gravitational wave detector LISA – that we take as reference – being at 20 nT/Hz at 0.1 mHz, and reaching an average 1.5nT/Hz at higher frequencies, from 100 mHz to 1 Hz.

Distributed optical fiber magnetic field sensor based on polarization-sensitive OFDR.

A distributed optical fiber magnetic field sensor based on a polarization-sensitive optical frequency domain reflectometer (POFDR) is proposed. It extracts the accumulated Faraday rotation by combining the Stokes vectors and the backward Mueller matrices from the measured states of polarization (SOPs) and obtains the magnetic field component. This method avoids adjusting the input polarization during the magnetic field sensing process. It overcomes the drawback of the conventional POFDR scheme, which requires at least two sets of different input SOPs for each sensing. Finally, the aforementioned effectiveness has been experimentally verified by using a single-mode sensing fiber. The results show that the sensor has good repeatability and linearity. The measurement error of the magnetic field sensor is 19.4 mT. The measured magnetic field variations agree with the applied ones with similarities higher than 0.98.

Temperature self-compensating photonic crystal fiber grating magnetic field sensor

Temperature self-compensating photonic crystal fiber grating magnetic field sensor

Highly sensitive magnetic field sensor using magnetic fluid filled dual-core photonic crystal fiber

A high sensitivity fiber optic magnetic field sensor that utilizes a dual-core photonic crystal fiber (DC-PCF) filled with magnetic fluid (MF) has been proposed and validated to simultaneously detect magnetic field intensity and temperature. DC-PCF is a multimode fiber that supports various modes of light transmission and induces intermodal interference within fiber core. The numerical analysis of the mode characteristics of DC-PCF is conducted. The sensing structure relies on the use of a DC-PCF with air holes filled with a suitable material, such as MF substance. The analysis of the working principle of the DC-PCF for sensing and measurement is conducted by considering its structural characteristics and mode characteristics. The effective refractive index (ERI) of MF is affected by external magnetic field intensity and temperature. To extract the effective frequency points, the fast Fourier transform (FFT) method can be employed. Additionally, the inverse fast Fourier transform (IFFT) method can be utilized to determine the magnetic field sensitivity, which can reach up to 1.562 nm/mT. Furthermore, the temperature sensitivity can be as high as −1.043 nm/°C. The sensor demonstrates excellent repeatability and showcases low detection limits of 0.0128 mT and 0.0192 °C, respectively. Additionally, the proposed sensor exhibits substantial potential for further development in the field of high sensitivity magnetic field detection applications.

Contactless current measurement for suspended overhead lines using a magnetic field sensor array

AbstractIn this study, a long‐distance non‐contact current measurement method is proposed based on the non‐contact sensor array measurement technology, combined with a new current algorithm. The sensor array is a vertical array composed of three three‐axis magnetic field (MF) sensors that is placed on the ground plane below the measured overhead line. The proposed current algorithm can optimize the geometry of the overhead line using the spatial MF values measured by the sensor array and then the three‐phase currents can be calculated. To improve the accuracy of current measurement, the spatial MF model in the algorithm considers the influence of cable sag. It enables a more accurate coupling matrix between the measured overhead line and the sensor array to be established. Additionally, the current algorithm architecture is designed using a composite algorithm to more optimally obtain the best three‐phase current values. A scale‐down overhead‐line measurement system is developed to test the proposed current measurement method. The results show whether a cable sag exists when the three‐phase currents are approximately balanced, with errors less than 2.0%. Moreover, it can be determined whether cable sag exists when the three‐phase currents are unbalanced, with less than 3.4% errors.

Wearable sensor-based on exercise monitoring system for disabled the individuals using a multi-attribute fuzzy evaluation mode

Recently, there has been a lot of interest in using the wearable sensors for tracking the exercise progress because of the unbiased accuracy and precision they are provided throughout the continual monitoring. For those with physical impairments, the system’s non-intrusive, lightweight ways of the monitoring activity may ease their load and enhance the quality of their decision-making. As a different measuring unit measures the exercise activity levels recorded by the each wearable sensor, it is challenging to assess the monitoring system. Hence, this paper proposes a Hybridized Fuzzy Multi-Attribute for Exercise Monitoring System (HFMA-EMS) to address the uncertainty issues of the wearable sensors. The Triangular Fuzzy membership function is proposed to begin classifying the observed values. Pair-wise attribute comparison and evaluator weighting in a T-spherical uncertain linguistic set setting utilizing the Techniques for Ordering of Preferences by Similarities to Ideal Solutions (TOPSIS). In the suggested method, a utility function is used to assess the merits of a model in which attribute the weights are calculated, followed by an exercise in which the attributes are ordered employing the Measurements of the Alternative and Ranking Compromise Solutions model (MARCOS). The performance is performed to analyze the proposed method’s accuracy, precision, recall, f1-score, and correct and incorrect exercise assessment by an accelerometer, gyroscope, and magnetic field sensor unit. The application scenario of the HFMA-EMS can be used in the clinical applications, healthcare management, and sports injury detection.

Tunable and switchable magnetoresistance of P3HT:PCBM organic framework

This letter demonstrates a multifunctional electronic device based on an organic multiferroic fabricated with newly synthesized polythiophenes and fullerene derivative polymers with crystal sizes in the millimeter and micrometer scales, respectively. The novelty of the presented framework is the insensitivity to the fabrication process and physical demonstration of organic multiferroics. Devices with drastically different functionalities were fabricated using the same processing steps. We demonstrate a non-contact magnetic field sensor based on magneto-resistivity. Remarkably, the same device exemplifies a magnetic data storage characteristics.

Three-Axis Vector Magnetometer with a Three-Dimensional Flux Concentrator.

This research proposes a magnetic field sensor with spatial orientation ability. Through the assistance of a magnetic flux concentrator, out-of-plane magnetic flux can be concentrated and guided into the planar magnetic cores of a fluxgate sensor. A printed circuit board is used to construct the basic planar structure, on which the proposed three-dimensional magnetic flux concentrator and magnetic cores are assembled. This reduces the alignment error of the coils and improves the reliability of the sensor. Three-axis sensing is achieved by using the second harmonic signals from selected sensing coil pairs. The magnetometer exhibits a linear range to 130 μT. At an excitation frequency of 50 kHz, the measured sensitivities are 257.1, 468.8, and 258.8 V/T for the X-, Y-, and Z-axis sensing modes, respectively. This sensor utilizes only one sensing mechanism for the vector field, making it suitable for IoT applications, especially for assessing mechanical posture or position.

Synthesis of the Spatial Arrangement of Magnetic Field Sensors for Active Magnetic Field Shielding Systems of Overhead Power Lines

The purpose of the work is to develop a synthesis method for the spatial and angular arrangement of magnetic field sensors in order to ensure maximum efficiency of a robust system for active shielding of the magnetic field generated by overhead power lines, and to reduce the sensitivity of the synthesized system to initial uncertainties in changes in the level of the initial magnetic field, as well as system parameters while working. To achieve this goal, the spatial location coordinates and angular position of all magnetic field sensors, controller parameters, and gain vector for the compensating windings are determined. A synthesis of the spatial location and angular position of magnetic field sensors is created to solve a minimax vector optimization problem in which the vector objective function is calculated based on the Biot-Savart’s law. Solution of the minimax vector optimization problem, calculated on the basis of optimization algorithms for a multi-swarm of particles from Pareto-optimal solutions, taking into account the parameters of binary relations. Significant results obtained on the basis of the developed synthesis method are the effectiveness of a robust active shielding system for magnetic fields generated, as a consequence, by power lines with a synthesized spatial arrangement and angular position of magnetic field sensors obtained in the process of theoretical and experimental research. The significance of the results lies in the fact that practical recommendations are given for the reasonable choice of spatial location and angular position of magnetic field sensors, the spatial arrangement of shielding windings of a robust magnetic field shielding system for various characteristics of power lines.

Использование техники подмоделирования для сокращения временных затрат моделирования дистанционных датчиков магнитного поля

Currently, various magnetic field sensors located at a distance from the signal source are widely used in technology. The development and optimization of the designs of such sensors is often carried out using computer modeling, which requires not only large computing resources, but also significant time costs. Thus, the development and application of special methods to reduce the time spent on modeling these converters are relevant. The solution of differential equations in the magnetic field model of the converter is performed using the finite element method implemented in the COMSOL Multiphysics program. The solution of the chain model is obtained based on the general provisions of the theory of circuits using the built-in electric circuit editor in the COMSOL Multiphysics program. The use of a submodeling technique is proposed to solve transient processes in magnetic field sensors with a magnetic circuit and located at a great distance from the signal source. It is proposed to use the solution of a two-dimensional model as initial conditions. A technique to determine the size of a submodel is presented by comparing the results of two two-dimensional models, one of which does not consider the magnetic circuit. The factors influencing the effectiveness of the proposed technique are determined. The developed submodel tuning technique reduces the simulation time of magnetic field sensors with an error of replacing the complete model with a submodel of no more than 1 %. Application of the proposed submodeling technique will improve the efficiency of the design of magnetic field sensors.

Transformation of topological states in three-dimensional photonic crystal under magnetic field modulation

The realization and modulation of high-order topological states in three-dimensional (3D) photonic crystals (PCs) hold great significance for practical applications in optical communication, optical information processing, and optical computing. However, they have encountered technological challenges due to the difficulty in achieving a complete bandgap in 3D PCs. To address this issue, we introduce a design for a 3D PC based on the Su–Schrieffer–Heeger (SSH) model that exhibits distinctive topological surface states, topological hinge states, and topological corner states. Furthermore, these three types of topological states can be interconverted through the modulation of magnetic field because the topological states are closed and extremely sensitive to the structure, which are modulated by the magnetic field. This intriguing capability holds potential applications in the manipulation of optical flow, optical signal storage, and magnetic field sensors.

A modern, rapid and simple investigation of Ampère’s law

Classical physics results are often taught purely from the theoretical side. Key results, especially in electromagnetism, are typically not explored experimentally, and in applications students are then expected to leap straight into more complex scenarios that make use of these principles in electronics, sensors and instrumentation. This is unfortunate because not all individuals are equally able to learn well purely from the mathematical angle, and even those who do are not exposed to exploring the magnitude of competing effects, for example isolating a particular magnetic field signal from the background of the Earth’s field. An experiment is presented here to test Ampère’s law with a setup that can be assembled out of everyday materials with minimal components—a smartphone, a DC power supply, wires—in a procedure that can be completed in just a few hours. The data from the three magnetic field sensors of the phones, together with the gyroscope sensors providing position, are recorded and numerically integrated. The experiment is also demonstrated using sensors collected by an Arduino board instead of a smartphone. The experiment allows to measure the net current carried by wires inside the closed path over which the magnetic field is integrated, i.e. Ampère’s law. This experimental approach to exploring Ampère’s Law can be adapted towards high school or university demonstrations, depending on the level of accuracy and detail that one aims to pursue.

Design and implementation of a temperature-insensitive heterogeneous resonant magnetic field sensor

A heterogeneous resonant magnetic field sensor is developed by using a FeGa plate, a quartz crystal double-ended tuning fork (DETF) resonator and a sapphire crystal plate. The double ends of the DETF are bonded to the ends of the magnetostrictive FeGa thin plate through two spacers, forming a resonant magnetic sensitive element. The C-cut sapphire crystal plate as a temperature compensation layer is bonded to the bottom of the magnetic sensitive element. When the temperature fluctuates, the bending deformation caused by the heterogeneous sensitive structure eliminates the thermal stress caused by the thermal expansion effect, thereby reducing the temperature drift of the sensor. The impact of different thicknesses of the sapphire substrate on reducing temperature drift in the sensor is analysed through theoretical calculation and finite element simulation. A sensor prototype was fabricated with a sapphire substrate thickness of 0.45 mm. The experimental results demonstrate that the temperature coefficient of frequency (TCF) of the sensor is reduced from 8.73 Hz/°C to 0.47 Hz/°C in the 0 °C to 60 °C range, and the sensitivity and resolution in the linear region of the sensor are 5.63 Hz/Oe and 42μOe (4.2nT), respectively.

A Combined Magnetoelectric Sensor Array and MRI-Based Human Head Model for Biomagnetic FEM Simulation and Sensor Crosstalk Analysis.

Magnetoelectric (ME) magnetic field sensors are novel sensing devices of great interest in the field of biomagnetic measurements. We investigate the influence of magnetic crosstalk and the linearity of the response of ME sensors in different array and excitation configurations. To achieve this aim, we introduce a combined multiscale 3D finite-element method (FEM) model consisting of an array of 15 ME sensors and an MRI-based human head model with three approximated compartments of biological tissues for skin, skull, and white matter. A linearized material model at the small-signal working point is assumed. We apply homogeneous magnetic fields and perform inhomogeneous magnetic field excitation for the ME sensors by placing an electric point dipole source inside the head. Our findings indicate significant magnetic crosstalk between adjacent sensors leading down to a 15.6% lower magnetic response at a close distance of 5 mm and an increasing sensor response with diminishing crosstalk effects at increasing distances up to 5 cm. The outermost sensors in the array exhibit significantly less crosstalk than the sensors located in the center of the array, and the vertically adjacent sensors exhibit a stronger crosstalk effect than the horizontally adjacent ones. Furthermore, we calculate the ratio between the electric and magnetic sensor responses as the sensitivity value and find near-constant sensitivities for each sensor, confirming a linear relationship despite magnetic crosstalk and the potential to simulate excitation sources and sensor responses independently.

One-step formation of three-dimensional interconnected T-shaped microstructures inside composites by orthogonal bidirectional self-assembly method

ABSTRACT The fillers inside a polymer matrix should typically be self-assembled in both the horizontal and vertical directions to obtain 3-dimentional (3D) percolation pathways, whereby the fields of application can be expanded and the properties of organic-inorganic composite films improved. Conventional dielectrophoresis techniques can typically only drive fillers to self-assemble in only one direction. We have devised a one-step dielectrophoresis-driven approach that effectively induces fillers self-assembly along two orthogonal axes, which results in the formation of 3D interconnected T-shaped iron microstructures (3D-T CIP) inside a polymer matrix. This approach to carbonyl iron powder (CIP) embedded in a polymer matrix results in a linear structure along the thickness direction and a network structure on the top surface of the film. The fillers in the polymer were controlled to achieve orthogonal bidirectional self-assembly using an external alternating current (AC) electric field and a non-contact technique that did not lead to electrical breakdown. The process of 3D-T CIP formation was observed in real time using in situ observation methods with optical microscopy, and the quantity and quality of self-assembly were characterized using statistical and fractal analysis. The process of fillers self-assembly along the direction perpendicular to the electric field was explained by finite element analogue simulations, and the results indicated that the insulating polyethylene terephthalate (PET) film between the electrode and the CIP/prepolymer suspension was the key to the formation of the 3D-T CIP. In contrast to the traditional two-step method of fabricating sandwich-structured film, the fabricated 3D-T CIP film with 3D electrically conductive pathways can be applied as magnetic field sensor.

Remote detection of the conductivity of current-carrying metallized traces

The weak magnetic fields generated by a current-carrying metallized traces are detected in view of their applications in bionic systems and neural-electrode interface technologies. The traces are formed by femtosecond laser processing of the surface of polydimethylsiloxane polymer substrate and further functionalization by electroless metallization. The measurements are performed by means of magneto-optical spectroscopy involving two optical beams, serving as pump and probe, where the magnetic field sensor is 87Rb atoms confined in a paraffin-coated optical cell. The experimental results show the feasibility of remote detection of the conductivity of metallized nickel traces.