Hall Element Research Articles

Flicker noise and magnetic resolution of graphene hall sensors at low frequency

Hall elements fabricated on chemical vapor deposited graphene exhibited high current- and voltage-related sensitivities due to its low intrinsic carrier density and high mobility about 5000 cm2/V s. Electric noise of the Hall elements was measured at room temperature and found to be largely Flicker noise at low frequency which can be well described by Hooge's empirical relation with a low noise parameter of about 1.8 × 10−4. The combination of high sensitivity and low noise in graphene Hall elements leads to a high room temperature magnetic resolution of about 5 × 10−3 G/Hz0.5 at 3 kHz.

Enhancement of anomalous Hall effect in Si/Fe multilayers

Anomalous Hall effect (AHE) studies were performed at 300 K on Si/Fe multilayers prepared by dc magnetron sputtering. About 60 times enhancement in the saturation Hall resistance and 80 times enhancement in anomalous Hall coefficient were obtained in [Si(50 Å)/Fe(tFe)]20 multilayers when decreasing the Fe layer thickness from 100 to 20 Å. The largest anomalous Hall coefficient (Rs) of 1.4 × 10−7 Ω m T−1 was found for tFe = 20 Å, which is about three orders of magnitude larger than that of pure Fe and Fe/Cr, Al/Fe, Cu/Fe, SiO2/FePt/SiO2 multilayers. The ordinary Hall coefficient R0 was about two orders of magnitude larger than that of pure Fe. The Rs was found to vary with the longitudinal electronic resistivity, ρ as Rsαρ2.2, indicating the role of interfaces for the enhancement of the AHE in the multilayers. An increase of Hall sensitivity from 9 mΩ T−1 to 1.2 Ω T−1 was observed on decreasing tFe from 100 to 10 Å. The high Hall sensitivity obtained was about three orders of magnitude larger than that of Al/Fe and Cu/Fe multilayers, showing it as an emerging candidate for Hall element for potential applications.

Miniature Hall sensor integrated on a magnetic thin film for detecting domain wall motion

We have fabricated a cross-bar Hall sensor made of 50-nm-wide and 100-nm-thick bismuth wires patterned by an electron-beam lithography and lift-off. The Hall coefficient at 300 K is as large as −0.44 cm3/C, yielding in a high product sensitivity of about 5 V/(A T). The series resistance was reduced as low as 1.7 kΩ with a short bar configuration, resulting in a high signal-to-noise ratio of 38.5 dB. These characteristics are far better than those reported with similar dimensions. The Hall element was successfully demonstrated for detecting the domain wall motion in an iron garnet film employed as the substrate.

유한요소법을 이용한 자기센서용 자속집속기의 해석

본 연구에서는 홀센서의 감도를 높이기 위해 사용되는 자속집속기의 두께, 홀소자와의 상대적 위치, 모서리 형상에 따르는 발생 자계를 유한요소법을 이용하여 계산하였다. 자속집속기의 두께가 얇을수록 발생 자계가 커지는 것을 알 수 있었고, 이 경향은 반자계를 고려한 겉보기 상대투자율의 두께의존성과 유사하다는 것을 알 수 있었다. 홀소자와의 상대적 위치에 따라 최대의 자계를 발생시키는 자속집속기의 최적의 두께가 변화하는 것을 알 수 있었다. 자속집속기와 홀소자의 간격이 가까울 경우, 자속집속기의 모서리 형상에 경사가 없는 것이 유리하지만, 자속집속기와 홀소자의 간격이 멀어질수록 자속집속기의 모서리를 경사지게 하는 것이 유리하다는 것을 알 수 있었다. In this study, magnetic concentrators which could be used to enhance sensitivity of Hall effect sensor were analyzed by using FEM. The parameters for FEM analysis were the thickness and edge shape of magnetic concentrator and relative position of magnetic concentrator against Hall element. Magnetic field in z direction decreased with increasing of the thickness of magnetic concentrator, of which tendency was similar to apparent relative permeability calculated with demagnetizing factor of magnetic concentrator. There were optimal thickness and edge shape of magnetic concentrator according to the relative position of magnetic concentrator against Hall element.

On the Controlling of Spherical Ultrasonic Motor

Research team of Prof. Shigeki TOYAMA has developed at Tokyo University of A&T a new type of ultrasonic motor. Its spherical shape confer 2 or 3 degree of freedom in a single joint which makes it suitable for mechatronics field. In order to control the Spherical Ultrasonic Motor a new method by using Hall sensors and a residual magnetic field induced in rotor was implemented. Present paper is dealing with the command and the control of a SUM by using Hall elements and a residual magnetic field induced in rotor. In this way the approach of controlling problem is by using the inverse kinematics and neuronal networks.

굴(Crassostrea gigas)의 패각운동을 이용한 생물모니터링시스템 연구 -I. 홀 소자를 이용한 저염분하에서 비정상적인 패각운동 측정

저염분에 따른 양식생물의 피해를 줄이기 위한 조기경보 방안으로 염분에 따른 굴(Crassostrea gigas) 패각운동 특성을 홀 소자를 이용하여 측정하는 생물모니터링시스템의 적용 가능성을 조사하였다. 염분농도 27 psu에서 굴의 패각운동은 평균 10-15 mm 정도의 개각상태를 유지하다가, 비교적 빠른 폐각상태를 지시하는 큰 파형이 보였으며, 다시 개각상태로 돌아가나, 그 속도는 폐각상태로 진행되는 속도보다 느리게 나타났다. 20 psu까지 저염분의 농도에서는 27 psu의 패각운동과 큰 변화가 없었다. 하지만 17 psu 이하의 염분농도부터 이상 패각운동이 지시되었으며, 10 psu에서는 패각운동이 없이 폐각상태를 유지하였다. 이와 같은 생물모니터링시스템을 패류 양식에 활용하여 해양환경의 이상변동을 신속히 감지할 수 있다면, 어업피해를 감소시킬 활동으로 연결될 것으로 기대된다.

The Design of Sport Bicycle Speed Odometer

As bicycle sport equipment, a sport bike needs a speed and distance measuring device, due to the characteristic of road cycling, thereby mastering the state of motion. According to external conditions such as temperature, wind speed, the bike can make the appropriate adjustment to achieve the best movement effect. The bicycle speed odometer is a major accessibility tool that satisfies with needs of the people with fast development. This study elaborated a bike speed odometer design based on Hall element, taking AT89C52 single chip as the core, measuring speed with A44E Hall sensor, to finish the bike mileage/speed measurement and statistics by displaying bike mileage and speed in real time. By using the Hall elements, the hardware of speed odometer input the number of pulse of per circle into the single-chip computer system. Then the signal processed by the single-chip computer displays. The software is programmed with assembly language and modular design idea. The design of the hardware circuit is simple and the subroutine has universal property, which fully meet the design requirements and possess a wide range of application and dissemination value.

Scalable fabrication of graphene devices through photolithography

Scalable fabrication of high quality graphene devices is highly desired and important for the practical applications of graphene material. Graphene devices are massively fabricated on SiO2/Si substrate through an efficient process, which combines large scaled growth of monolayer graphene on Pt foil, modified bubbling transfer and photolithography-based device fabrication. These graphene devices present yield up to 86% (70 out of 81), field-effect mobility around 2500 cm2 V−1 S−1 and Dirac point voltage near to 0 V, as well as a narrow performance metrics distribution. In addition, as-fabricated graphene Hall elements through this process exhibit high current sensitivity typically up to 1200 V/AT.

Batch-fabricated high-performance graphene Hall elements

Hall elements are by far the most widely used magnetic sensor. In general, the higher the mobility and the thinner the active region of the semiconductor used, the better the Hall device. While most common magnetic field sensors are Si-based Hall sensors, devices made from III-V compounds tend to favor over that based on Si. However these devices are more expensive and difficult to manufacture than Si, and hard to be integrated with signal-processing circuits for extending function and enforcing performance. In this article we show that graphene is intrinsically an ideal material for Hall elements which may harness the remarkable properties of graphene, i.e. extremely high carrier mobility and atomically thin active body, to create ideal magnetic sensors with high sensitivity, excellent linearity and remarkable thermal stability.

Design of Sensor Bearing Based on the Hall Elements

This paper describes a structure design of sensor bearing based on Hall element, the bearing by a Hall sensor and deep groove ball bearing, can measure speed of rotation, direction of rotation and acceleration signal etc. And with the Swedish SKF sensing bearing are compared, analyzes the bearing performance characteristics.

High Sensitivity InAs DQW Linear Hybrid Hall ICs with InAs Deep Quantum Well Hall Elements

SUMMARY By electrically connecting and placing an InAs deep quantum well (DQW) Hall element as a magnetic sensor chip and an Si IC linear amplifier in a small plastic package, a very small InAs DQW linear hybrid Hall IC (InAs DQW LHHIC) with a high magnetic field sensitivity has been developed. The output voltage of the hybrid Hall IC showed a very small temperature coefficient of 0.02%/°C and the response time was very low, less than 3 μs. By using this InAs DQW LHHIC, practical current sensors with high sensitivity, high accuracy, and temperature stability have been developed.

Design and Implementation of a Radial Magnetic Bearing With Permanent Magnet Bias

A new yoke winding for a radial magnetic bearing with permanent magnet bias flux is investigated and shown to reduce the copper loss and copper cost, by 32% in the prototype built. Magnetic circuit analysis neglecting fringing was found to give a poor estimate of the permanent magnet bias flux and 3D finite element analysis (FEA) would be needed to model it. However, 2D FEA was sufficient to model the magnetic field and force in the plane of the stator laminations, providing that the correct bias flux was imposed as a boundary condition. Solutions for the axial magnetic vector potential component Az were obtained, with a discontinuity prescribed across a cut from the inner to outer domain boundary. A small prototype was built and tested on a shaft whose other end was supported by a ball bearing race with free angular movement. For each of the horizontal and vertical directions, closed loop control was applied with Hall elements providing the shaft position signal. A lead-lag controller, designed using Matlab Simulink and implemented in Turbo Pascal 6, levitated the rotor.

室温下石墨烯的霍尔效应实验研究

The grapheme samples were deposited on glass substrates by chemical vapor deposition(CVD).Both the length and width of graphene samples were 1.23 cm,and the thickness was 3 atomic layer thickness setting scales.The Hall effects at room temperature of the samples were studied.There was good ohmic contact between the sample and the electrode.By using van der Pauw method,the Hall voltage of the samples were measured under the magnetic field strength 0.353 T and different electric currents.The calculating results show that the graphene Hall coefficient RH is 7.00×10-7 m3/C,the carrier concentration n is 10.52×1024/m3 and the Hall element production sensitivity KH is 6.87×102 m2/C.

Switchable Attenuation of Low Magnetic Fields for Integrated Vertical Hall Sensors Using a Ferromagnetic Layer

The typical measurement range of integrated Hall sensors lies between approximately 10 μ T and 10 T. Above that range, nonlinear effects occur due to an increasing Hall angle. Below that range, sensor offsets and noise corrupt measurements. Because of its geometry, vertical Hall elements exhibit considerably less sensitivity making them more susceptible to offset and noise. We present a method of attenuating external fields by using a coating of ferromagnetic material for the purpose of offset calibration. If the coating is driven into saturation by an integrated excitation wire, the external field becomes “visible” for the sensor and can be measured offset-free. As the integrated excitation wire is able to saturate the coating very locally the unsaturated regions of it may act as a concentrator of the external field and hence increases the sensitivity. Different materials and geometries were modelled and simulated with the finite element method (FEM) and the approach was tested for feasibility. The results of the simulations were used to design an experimental integrated circuit (IC) and to choose a suitable material for the coating layer. With this IC we tested the new sensor and obtained first results which are presented in this paper.

A technique for Detecting Hypoxic Seawater and Hypoxic Seawater Containing Hydrogen Sulfide by Monitoring Pearl Oyster Valve Movement Patterns with a Hall Element Sensor

A technique for Detecting Hypoxic Seawater and Hypoxic Seawater Containing Hydrogen Sulfide by Monitoring Pearl Oyster Valve Movement Patterns with a Hall Element Sensor

Winter quiescence and spring awakening of the Eastern oyster Crassostrea virginica at its northernmost distribution limit

To test the hypothesis that oysters, Crassostrea virginica, from the northernmost part of the species range in the Gulf of St. Lawrence (48°N) open their valves at lower temperatures than those reported for more southern oysters, Hall element sensors were used to monitor their gaping behaviour. These observations were made in a flow-through system and the temperature, salinity and relative fluorescence of unfiltered seawater were monitored. Photoperiod was controlled (15 h dark:9 h light) and light levels were measured but not closely controlled. Gaping behaviour was followed from February to June 2010 (113 days) and from April to May 2011 (34 days) and was classified into three successive phases: quiescent, awakening and active. Although valves were either closed or slightly open during the quiescent phase (maximum gape angle = 0.49°, SE = 0.04), they abruptly opened to maximum angles of about 5.88° (SE = 0.29) during the awakening phase. Moreover, there was noticeable synchrony amongst individuals, since approximately one-half of the monitored population awoke within a 6.6-h period in both study years. Correlative analyses identified temperature as a factor influencing valve movement, and oysters awakened when temperatures were 0.2–4.0 °C (mean = 2.2, SE = 0.2). Oysters exerted their maximal gape angle as soon as temperatures reached 2.8–6.6 °C (mean = 4.8, SE = 0.2). During the active phase, valves remained open 68.6 % (2010) and 79.7 % (2011) of the time. An unexpected result was the observation of a diurnal rhythm in valve openness whereby the openness was greatest near the end of the afternoon and least in the early morning.

Research of Non-Destructive Testing of Wire Rope Using Magnetic Flux Leakage

Based on the magnetic theory, the paper reviewed the factors of affecting the distribution of magnetic flux leakage (MFL) on the ferromagnetic material and analyzed the wire rope defects characters from MFL signal. A non-destructive testing (NDT) instrument of steel wire rope using magnetic flux leakage was presented in this paper. By using permanent magnets to magnetize wire rope and using Hall element arrays to test MFL, Intelligent signal processing was applied for effective discrimination of wire rope’s flaws. The experiment results show the degree and the width of defects, the annular distribution of localized flaws such as concentrated or dispersive broken wires can be well distinguished. The instrument can be used conveniently with good resolution and repeatability and can meet the requirement of real time.

Study on Dependence of Stress on the Hall Element Characteristics

Study on Dependence of Stress on the Hall Element Characteristics

Investigation of Array Magnetic Memory Testing Technology on Extension of Metal Crack

Metal Magnetic Memory (MMM) testing method has its own effective and unique advantages on the research of extension of metal crack. The array magnetic memory testing sensor designed and assembled in accordance with specific conditions, could evidently enhance testing-efficiency, such as for components with complex shape or large surface area, and may simplify the test equipment correspondingly. A kind of array magnetic memory sensor with Hall elements as core components was designed and an experiment on metal magnetic memory testing on extension of metal crack was executed. The experiment results indicate that the magnetic memory testing technique could effectively monitor and qualitatively evaluate the progress of metal crack extension.

Limiting Factors of Driving Hall Element by Pulsed Power Supply

The limiting facts of driving the Hall element by the pulsed power supply and sampling when the peak value coming are studied. The equivalent relation of temperature rising between the DC and pulsed power supply is given. When the electric field intensity inside the Hall element rises to about 1850V/cm, the linear relationship between the Hall output voltage and the input voltage will be affected by the decrease of the mobility. The thermal-power consumption almost does not affect the use of the Hall element. The above problem could be overcome by enlarging the die dimension.