Hall Element Research Articles

Neuromorphic alternating current sensing using piezoelectric resonators and physical reservoir computing

Non-contact current sensors are valuable because they can safely measure alternating current without interrupting the circuit. However, current sensors utilizing Hall elements or coils are only available for single wires, and piezoelectric resonator-based sensors have difficulty achieving both high sensitivity and linearity. To address this issue, we propose a novel approach, that is, the use of piezoelectric current sensors as nodes for physical reservoir computing (physical RC), allowing us to utilize nonlinear regions. To improve the sensitivity and short-term memory required by physical RC, a piezoelectric resonator with a quality factor of 75 was realized by employing a tuning fork structure. Nonlinearities were also introduced by analog circuits. The results of the benchmark tests indicate that the device worked as a physical RC and that it successfully predicted unknown current values from the results of training at three levels of current.

A High-Resolution Magnetic Field Imaging System Based on the Unpackaged Hall Element Array

We have designed a high-resolution magnetic field imaging system using 256 unpackaged Hall elements. These unpackaged Hall elements are arranged in a Hall linear array, and the distance between adjacent elements reaches 255 µm. The sensitivity of the unpackaged Hall element array can be adjusted using a computer to measure magnetic environments with different magnetic field strengths. High-resolution magnetic field images of 256 × 256 pixels can be generated by moving the array using the X–Y axis motorized rail. This spatial resolution can reach 99.61 pixels per inch (ppi). This rail allows for the spatial resolution of the system to be further increased to 199.22 ppi by using a special movement route. In the experiments, we employ this system to image magnetized metal scissors, and the result displays the structural features of the scissor surface. We also detected the magnetic suction wireless charging coil inside an Apple phone. The image obtained shows the shape of the coil and the gap between the magnets. The high-resolution magnetic imaging system displays the magnetic characteristics of the sample very well and easily obtains information about small-shaped structures and defects on the sample surface. This provides the system with potential in several fields such as quality inspection, security, biomedicine, and detection imaging.

An Advanced Hall Element Array-Based Device for High-Resolution Magnetic Field Mapping.

The precise mapping of magnetic fields emitted by various objects holds critical importance in the fabrication of industrial products. To meet this requirement, this study introduces an advanced magnetic detection device boasting high spatial resolution. The device's sensor, an array comprising 256 unpackaged gallium arsenide (GaAs) Hall elements arranged in a 16 × 16 matrix, spans an effective area of 19.2 mm × 19.2 mm. The design maintains a 1.2 mm separation between adjacent elements. For enhanced resolution, the probe scans the sample via a motorized rail system capable of executing specialized movement patterns. A support structure incorporated into the probe minimizes the measurement distance to below 0.5 mm, thereby amplifying the magnetic signal and mitigating errors from nonparallel probe-sample alignment. The accompanying interactive software utilizes cubic spline interpolation to transform magnetic readings into detailed two- and three-dimensional magnetic field distribution maps, signifying field strength and polarity through variations in color intensity and amplitude sign. The device's efficacy in accurately mapping surface magnetic field distributions of magnetic and magnetized materials was corroborated through tests on three distinct samples: a neodymium-iron-boron magnet, the circular magnetic array from a smartphone, and a magnetized 430 steel plate. These tests, focused on imaging quality and magnetic field characterization, underscore the device's proficiency in nondestructive magnetic field analysis.

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.

Characteristics of blood flow velocity in the radial artery and finger capillaries using magnetoplethysmogram and photoplethysmogram

The Hall element and optical sensor, which can detect the magnetic field change caused by the minute fluctuations of the permanent magnet according to the periodic movement of the radial artery and the light absorption and reflection intensity according to the change in wrist blood flow, respectively, are used as key elements in digital healthcare devices. The pulse waves of the radial artery inside the wrist were measured and analyzed using a clip-type pulsimeter, magnetoplethysmogram (MPG). The pulse wave, which is the change in blood flow obtained by photoplethysmogram (PPG), was measured on the dorsal side of the wrist or the fingers simultaneously with MPG. The ABFV (artery blood flow velocity) is a few ten cm/s as DH (distance between MPG and PPG) divided by ΔT(a) which is the time difference between the first peaks of MPG and PPG waveforms on the dorsal side of the wrist. The PBFV (peripheral blood flow velocity) is a few mm/s as LH (hand length) divided by ΔT(p), which is the time difference between the first peak of MPG waveform and the third peak PPG waveform on the finger. For four subjects of 20s, SPWV was approximately 0.98∼1.19 m/s, ABFV in the radial artery was approximately 0.40∼0.44 m/s, and finger capillary PBFV was approximately 6.3∼8.6 cm/s. These results show reasonable values similar to the blood velocity of many blood vessels flowing through the human body.

(Invited) Magneto-Mechanical Micro-Nano Devices with Electrodeposited Magnetostriction Films

Microsystems play an important role in IoT sensors and actuators in the recent information and communication society. Among these, actuators are important elements used in transmitters, acoustic devices, and optical elements, and for those devices, piezoelectric thin films have been used widely. Magnetostrictive materials are expected to have even greater actuation performance than that of the piezoelectric films, but in the magnetostrictive films integration technologies with a high performance have not yet been fully developed. We have developed the film deposition technologies for magnetostriction materials by electrodeposition and apply them to actuators and sensors [1,2]. The FeGa, TbDyFe, and FeCo magnetic materials are known as giant magnetostriction materials [3]. In this study, the film deposition method for these materials have been developed by electrodeposition. Tbe electrodeposition of rare earth elements is generally considered to be difficult, but in this study, by using Fe chelate as a catalyst, the magnetic films containing Fe and rare earth elements have been successfully deposited, and large magnetostriction are achieved. The TbDyFe films show magnetostriction of ~1000 [1]. In addition, large volume magnetostriction has been observed in these amorphous materials. The magnetostrictive materials are known to have a reverse magnetostriction effect, in which the magnetization of the magnetic material changes when it is subjected to strain. They are known to work as strain sensors based on magnetic measurements. In order to demonstrate the strain sensing, a bi-material cantilever of FeGa/Si with a Si Hall sensor integrated on the support has been developed, as shown in Fig. 1 [2]. The vibration of the cantilever can be detected from the magnetization change using the integrated Hall sensor. On the other hand, magnetostrictive actuators generally require an electromagnet to drive them, making them difficult to miniaturize the system. Therefore, an attempt has been made to drive magnetostrictive thin films by injecting spins into them using the spin Hall effect, giving angular momentum to the spins of magnetic materials and changing the spin fluctuations [4]. It is found that a large strain can be generated by spin injection into the TbDyFe film. The above results show that high-performance magnetostrictive films can be deposited by electrodeposition and can be applied to strain sensors and spin-current driven actuators, and are expected to be applied to the development of novel sensors and actuators [5].References H. Shim, K. Sakamoto, N. Inomata, M. Toda, N. V. Toan and T. Ono, Magnetostrictive Performance of Electrodeposited TbxDy(1−x)Fey Thin Film with Microcantilever Structures, Micromachines 11, 5 (2020) 523.T. Ezura, N. Inomata, T. Ono, Integration of Magnetostrictive Microsensor With Hall Element for Microstructure Resonant Detection, 21st International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers), (2021) 418-421.Mohammad Akita Indianto, Masaya Toa, Takahito Ono, Comprehensive study of magnetostriction-based MEMS magnetic sensor of a FeGa/PZT cantilever, Sensors and Actuators A 331, (2021) 112985.H. Arisawa, H. Shim, S. Daimon, T. Kikkawa, Y. Oikawa, S. Takahashi, T. Ono, E. Saitoh, Observation of spin-current striction in a magnet, Nature Communication 13 (2022) 2400.M. A. Indianto, M. Toda, T. Ono, Development of assembled microchannel resonator as an alternative fabrication method of a microchannel resonator for mass sensing in flowing liquid, Biomicrofluidics 14, (2020) 064111. Figure 1

Heterocosmica на киното

The paper argues for the advantages of using the full format of the art form “cinema” over its more abstract version “film”. To this end, the heterocosmic nature of the “moving image” in cinema is pointed out and its aspects are analysed phenomenologically. A phenomenology of the cinema hall, the spectator, the actor, the objects and other pleromatic elements is made.

Research on multi-sensor positioning and number identification method of greenhouse based on hall effect

Wireless sensors are becoming increasingly important in greenhouse automation. In order for wireless charging to be as effective and stable as possible, accurate spatial physical location information and sensor quantity information are essential. Consequently, identifying sensor location and quantity information has become a crucial step in the construction of a high-quality greenhouse wireless charging system. This paper suggests using the Hall effect for multi-sensor positioning and quantity identification to solve this issue. The multi-sensor greenhouse space with Hall elements is modeled physically in three dimensions, with theoretical research and equation development. A magnetic field simulation using Maxwell is conducted to compare the magnetic field for sensor localization in space, and the parameters of the designed 3D physical model is optimized based on the simulation. Comparative experiments on sensor positioning and quantity identification were also carried out, and the design parameters constructed the experimental verification platform. After that, numerous sets of experimental comparison data were collected to confirm the system's viability. Finally, the positioning experiment's error between the calculated and test values is 5 to 11 percent, and the number of the receivers can be accurately obtained based on the number of Hall voltage pulse responses. The concept of multi-sensor positioning and number identification based on the Hall effect serves as a model and a direction for future research on wireless charging in greenhouses and other environments.

A Comprehensive Review of Steel Wire Rope Degradation Mechanisms and Recent Damage Detection Methods

Steel wire ropes are the vital load-bearing element in many rope transport devices, such as mine hoists, personal lifts, bridges and cableways. Non-destructive fault detection is a crucial issue for safety and reliability. This paper presents a comprehensive review covering three areas: damage mechanisms for steel wire ropes, physical phenomena used for diagnostics of steel wire ropes and practical applications of magnetometers. The advantages and disadvantages of each group of sensors, such as the induction coil, Hall element, magnetoresistance and optically pumped magnetometers, are presented. The author indicates the direction of the development of signal analysis techniques. In summary, the challenges and future directions for the development of wire rope flaw detection in practical applications are presented, especially considering the future of passive magnetic methods.

Speed Measurement Method for Moving Conductors Based on Motion-Induced Eddy Current

Speed measurement plays an important role in many measurement and control systems in industry. A simple and efficient speed measurement method for smooth conductive specimens based on motion-induced eddy currents is studied in this paper. The speed sensor consists of a magnet and a Hall element. When the conductor moves beneath the magnet, eddy currents are generated, which further generate a secondary magnetic field that is dependent on the moving speed of the conductor. The Hall element picks up this field to determine the relative speed between the conductor and the sensor. First of all, a 2D analytical model for the induced eddy currents and corresponding magnetic fields has been proposed by solving the Maxwell’s equations using spatial Fourier transforms. Then, the change in current density and magnetic field with conductor speed is analyzed using both the analytical model and the finite element method. Speed sensing experiments were conducted on a rotating conductive disk, the results showed good agreement with the proposed analytical model. Finally, specifications such as accuracy, repeatability, linearity, and resolution of the prototype sensor have been tested.

Magneto-Optical Probe With Integrated Optical Elements for Measuring Environmental Magnetic Fields in the Low- and Intermediate-Frequency Bands

In recent years, development of devices using magnetic fields in the low frequency bands (DC to 100 kHz) and intermediate frequency bands (300 Hz to 10 MHz) is progressing. The influence of magnetic fields generated from such devices on human body is drawing attention. Responding to the requirement to construct measurement system with ability to measure wide band frequency range for evaluating such magnetic fields, the authors have developed a prototype of the new measurement system, measuring environmental magnetic fields from DC to 20kHz, and confirmed its performance. It is confirmed that the output signal from the conventional magneto-optical probe (MO probe) fluctuates when the optical fiber cable is bent between the polarizer, probe, and analyzer. Therefore, it is proposed that the polarizer and analyzer are miniaturized and integrated into the body of MO probe, optical fiber cables inside the housing are fixed. The output signal from the new MO probe do not fluctuate when optical fiber cables outside the housing are bent. Furthermore, the measurement system using this MO probe is examined under applied magnetic fields from DC to 20kHz. Similar signals are observed both in voltage signals obtained by the new measurement system and in magnetic field signals measured by the Hall element type magnetic field probe. In addition, a comparison with existing sensors and an example of the application of this measurement system to the measurement of magnetic fields generated by power equipment are shown.

Research on Theory and Simulation of Magnetic Liquid Micro Differential Pressure Sensor

With magnetic liquid micro differential pressure sensor as the research object, using the finite element analysis software COMSOL, magnetic liquid micro differential pressure sensor are analyzed and calculated by first hall element in the location of the magnetic field change curve, and then analyzed the magnetic liquid micro differential pressure sensor restoring force curve, analyzes the three different change trend of the spacing between the initial magnetic field force, And the change equation of magnetic force is fitted. Finally, the pressure resistance of the magnetic liquid micro-differential pressure sensor is calculated to ensure the integrity of the magnetic liquid sealing ring in the range of measurement, so that it has good sealing performance. The results show that when the distance between two cylindrical permanent magnets L=10mm, the magnetic flux density B at the central axis changes approximately linearly with the distance. The recovery force curve of permanent magnet has good linearity in the spacing range of 24mm ~ 40mm. The sensor has a four-stage magnetic liquid sealing ring, the overall pressure resistance value is four times the unilateral pressure resistance capacity, the theoretical pressure resistance value of magnetic liquid is 5000Pa.

Design and Test of A Force Feedback Seedling Pick-Up Gripper for An Automatic Transplanter

Aiming at the problems of seedling injury and planting leakage due to the lack of seeding clamping force detection and real-time control in vegetable transplanting, a force feedback gripper was developed based on the linear Hall element. The mechanical properties of the stem of pepper cavity seedlings were first analyzed to provide a basis for the design of the gripper. A linear Hall sensor, a magnet, an elastic actuator, and an Arduino Uno development board make up the grasping force detecting system. Upon picking up a seedling, the elastic actuator, which is connected to the magnet, bends like a cantilever beam. As a result of the micro-displacement created by the elastic actuator, the Hall sensor’s voltage changes and can be used to determine the clamping force. Detection avoids direct contact between the sensor and the cavity seedlings, reducing the risk of sensor damage. Finite element method (FEM) simulations were used to determine the initial spacing between the magnet and Hall sensor and the effect of the elastic actuator. Control commands are sent to the servo based on the gripping force collected by the Arduino Uno board. Finally, the functions of accurate measurement, display, storage, and control of the clamping force of the cavity tray seedlings are realized, so that the damage rate of the cavity tray seedlings is reduced. In order to explore the influence of the elastic actuators on the clamping force detection system and the performance of the force feedback gripper, a calibration test of the clamping force detection system and a test of the indoor transplantation of pepper seedlings were carried out. Based on the calibration test, the clamping force detection system has a sensitivity of 0.0693 V/N, linearity of 3.21%, an average linear coefficient of determination of 0.986, and a range of 10 N, which fully meet the clamping force detection accuracy requirements during transplantation. Indoor tests showed that the force feedback gripper was stable and adaptable. This study can provide a reference for detecting and controlling clamping forces during transplantation.

A Review of Magnetic Flux Leakage Nondestructive Testing.

Magnetic flux leakage (MFL) testing is a widely used nondestructive testing (NDT) method for the inspection of ferromagnetic materials. This review paper presents the basic principles of MFL testing and summarizes the recent advances in MFL. An analytical expression for the leakage magnetic field based on the 3D magnetic dipole model is provided. Based on the model, the effects of defect size, defect orientation, and liftoff distance have been analyzed. Other influencing factors, such as magnetization strength, testing speed, surface roughness, and stress, have also been introduced. As the most important steps of MFL, the excitation method (a permanent magnet, DC, AC, pulsed) and sensing methods (Hall element, GMR, TMR, etc.), have been introduced in detail. Finally, the algorithms for the quantification of defects and the applications of MFL have been introduced.

Multisensor Fusion Time–Frequency Analysis of Thruster Blade Fault Diagnosis Based on Deep Learning

With the rapid development of marine robots, detecting abnormalities in propulsion systems is important during sailing as the unperceived damage of thrusters and propellers can cause substantial losses. In this study, different fault conditions of blades, including healthy, fully broken, half-broken, and simulated biofouling, are discussed. Current and sound signals are collected by a Hall element and hydrophone, respectively, to diagnose the propeller under different rotating speeds. The experiments include an ideal condition (swimming pool) and a noisy condition (lake). The raw data of time-domain signals are transformed into a time–frequency domain and shown as an image. A modified convolutional neural network (CNN) based on merging two signals is proposed to classify the faults. To compare the performance of models, the networks use single and multiple signals as input. The results demonstrate that the proposed multiple signals method achieves the best propeller fault diagnosis results, particularly when two signals are first trained separately and then merge at the end (99.94% in a swimming pool and 99.06% in a lake). Finally, the model was applied to Nvidia Jetson TX2 to verify the computing performance of an embedded system.

Application of single Hall chip in short circuit current detection of DC system

For the short circuit current test requirement of copper platoon at the entrance of a hybrid current-limiting fuse, the magnetic field distribution simulation model of copper platoon in both steady and transient current state were built. The influence of external magnetic field of copper platoon on the sensor measurement accuracy were analyzed in steady and transient state current. COMSOL simulation software was used to find the intersection point of magnetic induction intensity corresponding to steady-state and transient-state current with amplitude of 10 kA to determine the installation position of Hall element. In order to ensure the measurement accuracy, the installation position of Hall element was optimized by adding ferromagnetic materials, and the method of the final installation position of Hall element was obtained and verified by experiments. It was indicated that the simulation results was well consistent with the experiment results, which verified the correctness of the finite element model and the feasibility of the design. This design reduces the error of hall current sensor from 37% to 3.5%, which can be used as a reference for the research and development of small DC hybrid fuse.

High Performance Hall Sensors Built on Chemical Vapor Deposition-Grown Bilayer Graphene.

Graphene has been considered as an excellent channel material for constructing magnetic sensors or Hall elements with high sensitivity and linearity. Compared to intensively reported graphene Hall elements (GHEs) fabricated on monolayer graphene, the exploration on bilayer graphene-based Hall elements is very rare. Here, we first investigate the performance and potential of Hall elements built on chemical vapor deposition-grown bilayer graphene. Without applying any gate voltage, the bilayer GHEs exhibit a typical voltage sensitivity of 119 mV/VT and current sensitivity of 397 V/AT, which are higher than those in the monolayer GHEs, indicating the better performance in practical applications. Moreover, the bilayer GHEs present obviously lower noise and then the minimum detection magnetic field compared to the monolayer ones. Hall elements built on bilayer graphene show certain unique advantages and can be used as an important supplement to mainstreaming monolayer GHEs.

Magnetic-based detection of muscular contraction for controlling hand prosthesis

Muscle contraction information from the residual upper-limb of an amputee can generate intention-based control to prosthetic devices. There are several approaches such as electromyography (EMG), force myography (FMG), and mechanomyography (MMG) that can directly or indirectly measure muscular contractions. However, these techniques suffer from the problems like ambient noise, motion artifacts, inappropriate contact with the skin, inaccurate output, and high cost of measurement. In this work, a novel magnetic-based Hall myography (HMG) technique is introduced that can precisely measure the muscular contractions from the subject's upper-limb. The sensor setup consists of a magnetic coupler and Hall element assembly separated by a mechanical spring. Any contraction from the muscle produces gradual movement of the magnet towards the hall element. This change in displacement is sensed by the hall element and is then translated to a 0–5 V linear output using appropriate preprocessing hardware and software. The sensor performance was evaluated in terms of sensitivity, repeatability, hysteresis, and frequency response. In detecting muscle contractions from the forearm of subjects, the sensor showed highly correlated output (r > 0.94, p-value<0.0001) with the EMG sensor. Moreover, the sensor showed better signal stability and similar dynamic behavior as compared to the EMG sensor. Further, the utility of the sensor was tested for controlling hand prosthesis. Subjects wearing the sensor were able to control the flexion of prosthetic hand fingers proportionally according to their intensity of muscle contraction. With several advantages, Hall myography can replace the EMG technique for prosthesis control application.

Algorithm Research on the Conductor Eccentricity of a Circular Dot Matrix Hall High Current Sensor for ITER

To meet the high current measurement requirements of the international thermonuclear experimental reactor polar field (ITER PF) power supply, a noncontact dot matrix Hall high current sensor without a magnetic core is designed. Due to the existence of installation error, the measurement accuracy will be reduced due to conductor eccentricity in practical use. To solve this problem, this article will take the circular dot matrix Hall current sensor composed of eight Hall elements as an example and note the shortcomings of the two algorithms by analyzing the numerical integration algorithm and conductor positioning algorithm. Based on the two algorithms, a digital signal processing (DSP) conditioning algorithm is proposed. The DSP conditioning algorithm detects the output voltage of each Hall element after conductor offset and adjusts the output voltage of each Hall element by self-feedback, which simplifies the complexity of algorithm operation and eliminates conductor eccentricity error at the same time. Through simulation and field measurement verification, DSP self-feedback conditioning of the Hall element output voltage can eliminate the influence of conductor eccentricity error and improve the measurement accuracy of the sensor.

AUTOGENERATOR PARAMETRIC SENSORS OF THE MAGNETIC FIELD WITH A HALL ELEMENT AND A TWO-COLLECTOR BIPOLAR MAGNETOTRANSISTOR

Self-oscillating parametric magnetic field sensors with a frequency output signal based on transistor structures with negative differential resistance with primary magnetically sensitive Hall elements and a bipolar two-collector magnetically sensitive transistor are proposed, moreover, the primary magnetically sensitive elements also act as active circuit elements. Magnetic field sensors with a frequency output do not require analog-to-digital converters and amplifying devices for further processing of information signals, which reduces the cost of information-measuring equipment, in addition, it is possible to transmit information over a distance when the sensors operate at microwave frequencies. Based on the analysis of physical processes in primary magnetically sensitive elements and self-oscillators, mathematical models of sensors were developed, on the basis of which parametric dependences of the conversion and sensitivity functions were obtained. The obtained functions clearly show the influence of each element of the primary magnetic converters and self-oscillator elements on the output frequency of the sensors in comparison with the calculations of the conversion functions from equivalent device circuits based on the Kirchhoff solution equations. It is shown that the main contribution to the conversion functions is made by a change in the magnetic induction, which causes a change in the negative differential resistance and the equivalent capacitance of the oscillatory circuit of the self-oscillator, which in turn changes the output frequency of the magnetic field sensors. Self-oscillating parametric magnetic field sensors with a frequency output signal can significantly improve the accuracy and sensitivity of measuring magnetic induction, abandon analog-to-digital converters and amplifying devices in the further processing of information signals, they also allow transmitting initial information over a distance when operating at microwave frequencies. The sensitivity of the magnetic field sensors varies from 1.45 kHz/mT to 11.95 kHz/mT when the magnetic induction changes from 0.1 to 120 mT.