The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
David A Horsley - One of the best experts on this subject based on the ideXlab platform.
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dual resonator mems Lorentz Force magnetometer based on differential frequency modulation
2017 IEEE International Symposium on Inertial Sensors and Systems (INERTIAL), 2017Co-Authors: Soner Sonmezoglu, Thomas W Kenny, Ian B Flader, Yunhan Chen, Dongsuk D Shin, David A HorsleyAbstract:This paper presents a new dual-resonator MEMS magnetic sensor utilizing the Lorentz Force. Sensor operation is demonstrated using quadrature frequency modulated (QFM) readout, where the magnetic field strength is measured by monitoring the change in oscillation frequency. The Lorentz Force sensor, comprising of a matched pair of differentially operated closed-loop resonators on the same silicon die, produces two similar oscillation frequencies with nearly identical temperature sensitivities, providing a temperature-compensated FM output. The frequencies of the two oscillators are experimentally demonstrated to track each other over temperature, reducing the maximum drift error by a factor of 27 to ±2.2 µT, improving the sensor's bias instability from 170 nT to 63 nT, and increasing the averaging time to reach the bias instability from 0.3 s to 1.1 s. With 1 mA bias current, the device has a measured sensitivity of 2180 Hz/T and Brownian-noise-limited resolution of 60 nT/√Hz which is comparable to, or even better than, that of Hall-effect sensors available today.
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extended bandwidth Lorentz Force magnetometer based on quadrature frequency modulation
IEEE\ ASME Journal of Microelectromechanical Systems, 2015Co-Authors: Soner Sonmezoglu, David A HorsleyAbstract:In this paper, a Lorentz Force magnetometer demonstrates quadrature frequency modulation operation. The Lorentz Force magnetometer consists of a conventional 3-port resonator, which is put into oscillation by electrostatic driving and sensing. The bias current flowing through the resonator is proportional to the displacement, and generates Lorentz Force in quadrature with the electrostatic Force. As a result, the Lorentz Force acts as an equivalent spring and the magnetic field can be measured by reading the change in oscillation frequency. The sensor has a sensitivity of 500 Hz/T with a short-term noise floor of 500 nT $\surd $ Hz. The bandwidth of the sensor is increased to 50 Hz, a factor of 12 greater than that of the same resonator operating in amplitude-modulated mode. The short-term noise floor within 50-Hz bandwidth is comparable with CMOS Hall-effect sensors.
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Force rebalanced Lorentz Force magnetometer based on a micromachined oscillator
Applied Physics Letters, 2015Co-Authors: Soner Sonmezoglu, David A HorsleyAbstract:This paper presents a 3-axis Lorentz Force magnetometer based on an encapsulated micromechanical silicon resonator having three orthogonal vibration modes, each measuring one vector component of the external magnetic field. One mode, with natural frequency (fn) of 46.973 kHz and quality factor (Q) of 14 918, is operated as a closed-loop electrostatically excited oscillator to provide a frequency reference for 3-axis sensing and Lorentz Force generation. Current, modulated at the reference frequency, is injected into the resonator, producing Lorentz Force that is centered at the reference frequency. Lorentz Force in the first axis is nulled by the oscillator loop, resulting in Force-rebalanced operation. The bandwidth and scale-factor of this Force-rebalanced axis are independent of resonator Q, improving the sensor's temperature coefficient from 20 841 ppm/ °C to 424 ppm/ °C. The frequencies of the other two modes are closely spaced to the first mode's reference frequency and are demonstrated to track thi...
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Frequency-modulated Lorentz Force magnetometer with enhanced sensitivity via mechanical amplification
IEEE Electron Device Letters, 2015Co-Authors: Mo Li, Shmuel Nitzan, David A HorsleyAbstract:This letter presents a micromachined silicon Lorentz Force magnetometer, which consists of a flexural beam resonator coupled to current-carrying silicon beams via a microleverage mechanism. The flexural beam resonator is a Force sensor, which measures the magnetic field through resonant frequency shift induced by the Lorentz Force, which acts as an axial load. Previous frequency-modulated Lorentz Force magnetometers suffer from low sensitivity, limited by both fabrication restrictions and lack of a Force amplification mechanism. In this letter, the microleverage mechanism amplifies the Lorentz Force, thereby enhancing the sensitivity of the magnetometer by a factor of 42. The device has a measured sensitivity of 6687 ppm/(mA · T), which is two orders of magnitude larger than the prior state-of-the-art. The measured results agree with an analytical model and finite-element analysis. The frequency stability of the sensor is limited by the quality factor (Q) of 540, which can be increased through improved vacuum packaging.
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single structure 3 axis Lorentz Force magnetometer with sub 30 nt hz resolution
International Conference on Micro Electro Mechanical Systems, 2014Co-Authors: Vu A Hong, Chae Hyuck Ahn, Yushi Yang, Thomas W Kenny, David A HorsleyAbstract:This work demonstrates a 3-axis Lorentz Force magnetometer for electronic compass purposes. The magnetometer measures magnetic flux in 3 axes using a single structure. With 1 mW power consumption, the sensor achieves sub-30 nT/√Hz resolution in each of the 3 axes. Compared to the 3-axis Hall sensors currently used in smartphones, the 3-axis magnetometer shown here has the advantages of 10× lower noise floor and the ability to be co-fabricated with MEMS inertial sensors.
André Thess - One of the best experts on this subject based on the ideXlab platform.
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Lorentz Force particle analyzer
Journal of Applied Physics, 2016Co-Authors: Xiaodong Wang, André Thess, Rene Moreau, Yanqing Tan, Shangjun Dai, Zhen Tao, Wenzhi Yang, Bo WangAbstract:A new contactless technique is presented for the detection of micron-sized insulating particles in the flow of an electrically conducting fluid. A transverse magnetic field brakes this flow and tends to become entrained in the flow direction by a Lorentz Force, whose reaction Force on the magnetic-field-generating system can be measured. The presence of insulating particles suspended in the fluid produce changes in this Lorentz Force, generating pulses in it; these pulses enable the particles to be counted and sized. A two-dimensional numerical model that employs a moving mesh method demonstrates the measurement principle when such a particle is present. Two prototypes and a three-dimensional numerical model are used to demonstrate the feasibility of a Lorentz Force particle analyzer (LFPA). The findings of this study conclude that such an LFPA, which offers contactless and on-line quantitative measurements, can be applied to an extensive range of applications. These applications include measurements of the cleanliness of high-temperature and aggressive molten metal, such as aluminum and steel alloys, and the clean manufacturing of semiconductors.
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Lorentz Force Eddy Current Testing: a Prototype Model
Journal of Nondestructive Evaluation, 2012Co-Authors: Robert P. Uhlig, Hartmut Brauer, André ThessAbstract:We report an investigation of the motion of a free-falling permanent magnet in an electrically conducting pipe containing an idealized defect. This problem represents a highly simplified yet enlightening version of a method called Lorentz Force eddy current testing which is a modification of the traditional eddy current testing technique. Our investigation is a combination of analytical theory, numerical simulation and experimental validation. The analytical theory allows a rigorous prediction about the relation between the size of the defect and the change in falling time which represents the central result of the present work. The numerical simulation allows to overcome limitations inherent in the analytical theory. We test our predictions by performing a series of experiments. We conclude that our theory properly captures the essence of Lorentz Force eddy current testing although a refinement of the experiment is necessary to reduce the discrepancy to the predictions. In spite of its apparent simplicity the present system can serve as a prototype and benchmark for future research on Lorentz Force eddy current testing.
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flow rate measurement of weakly conducting fluids using Lorentz Force velocimetry
Measurement Science and Technology, 2012Co-Authors: Andre Wegfrass, Christian Resagk, Michael Werner, Bernd Halbedel, Thomas Frohlich, Christian Diethold, André ThessAbstract:We present a novel application of a contactless flow measurement system and validate its feasibility on an electrolyte pipe flow. The device relies on the technique of Lorentz Force velocimetry (LFV). LFV operates without any contact to either the fluid or the surrounding pipe walls. This is advantageous if the fluid under consideration is hot and aggressive, like a glass melt for example. Glass melts, however, have a very low electrical conductivity, resulting in Lorentz Forces in the micronewton range. In order to resolve these tiny Forces, we developed a measurement system based on the principle of deflection. Experiments on an electrolyte flow with an electrical conductivity of less than 20 S m −1 prove to be successful and to agree well with numerical simulations, and therefore show for the first time the applicability of LFV for fluids of such low conductivities.
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Lorentz Force sigmometry a contactless method for electrical conductivity measurements
Journal of Applied Physics, 2012Co-Authors: Robert P. Uhlig, Hartmut Brauer, Marek Ziolkowski, Mladen Zec, André ThessAbstract:The present communication reports a new technique for the contactless measurement of the specific electrical conductivity of a solid body or an electrically conducting fluid. We term the technique “Lorentz Force sigmometry” where the neologism “sigmometry” is derived from the Greek letter sigma, often used to denote the electrical conductivity. Lorentz Force sigmometry (LoFoS) is based on similar principles as the traditional eddy current testing but allows a larger penetration depth and is less sensitive to variations in the distance between the sensor and the sample. We formulate the theory of LoFoS and compute the calibration function which is necessary for determining the unknown electrical conductivity from measurements of the Lorentz Force. We conduct a series of experiments which demonstrate that the measured Lorentz Forces are in excellent agreement with the numerical predictions. Applying this technique to an aluminum sample with a known electrical conductivity of rAl ¼ 20:4MS=m and to a copper sample with rCu ¼ 57:92MS=m we obtain rAl ¼ 21:59MS=m and rCu ¼ 60:08MS=m, respectively. This demonstrates that LoFoS is a convenient and accurate technique that may find application in process control and thermo-physical property measurements for solid and liquid conductors. V C 2012 American Institute of Physics.
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Lorentz Force Flowmeter for Liquid Aluminum: Laboratory Experiments and Plant Tests
Metallurgical and Materials Transactions B, 2011Co-Authors: Yurii Kolesnikov, Christian Karcher, André ThessAbstract:This article aims to demonstrate that molten metal flow at a high temperature can be measured effectively in a contactless manner by using external direct current magnetic fields. The device applied in the present work is termed Lorentz Force flowmeter (LFF) and is based on exposing the flow to a magnet system and measuring the drag Force acting on it. Two series of measurements are reported. In the first series, we perform a model experiment in the laboratory using the eutectic alloy GaInSn, which is liquid at room temperature. The second series of measurements is devoted to two plant tests on flow measurement of a liquid aluminum alloy. In both tests, the Force acting on the magnet system is measured that is equal to the Lorentz Force acting on the flow. To generalize our results, we also derive the scaling law that relates the Force acting on a localized magnet system to the flow rate of a fluid with arbitrary electrical conductivity. This law shows that LFF, if properly designed, has a wide range of potential applications in ferrous and nonferrous metallurgy.
Cyril Lafon - One of the best experts on this subject based on the ideXlab platform.
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Acousto-electrical speckle pattern in Lorentz Force electrical impedance tomography
Physics in Medicine and Biology, 2015Co-Authors: Pol Grasland-mongrain, José María Navarro Marí, Stefan Catheline, Francois Destrempes, Jean-yves Chapelon, Remi Souchon, Cyril Lafon, Guy CloutierAbstract:Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz Force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz Force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz Force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz Force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an " acousto-electrical speckle " in the Lorentz Force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging.
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Lorentz Force electrical impedance tomography
arXiv: Medical Physics, 2014Co-Authors: Pol Graslandmongrain, Jean-yves Chapelon, Jean Martial Mari, Cyril LafonAbstract:This article describes a method called Lorentz Force Electrical Impedance Tomography. The electrical conductivity of biological tissues can be measured through their sonication in a magnetic field: the vibration of the tissues inside the field induces an electrical current by Lorentz Force. This current, detected by electrodes placed around the sample, is proportional to the ultrasonic pressure, to the strength of the magnetic field and to the electrical conductivity gradient along the acoustic axis. By focusing at different places inside the sample, a map of the electrical conductivity gradient can be established. In this study experiments were conducted on a gelatin phantom and on a beef sample, successively placed in a 300 mT magnetic field and sonicated with an ultrasonic transducer focused at 21 cm emitting 500 kHz bursts. Although all interfaces are not visible, in this exploratory study a good correlation is observed between the electrical conductivity image and the ultrasonic image. This method offers an alternative to detecting pathologies invisible to standard ultrasonography.
Jean-yves Chapelon - One of the best experts on this subject based on the ideXlab platform.
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Acousto-electrical speckle pattern in Lorentz Force electrical impedance tomography
Physics in Medicine and Biology, 2015Co-Authors: Pol Grasland-mongrain, José María Navarro Marí, Stefan Catheline, Francois Destrempes, Jean-yves Chapelon, Remi Souchon, Cyril Lafon, Guy CloutierAbstract:Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz Force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz Force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz Force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz Force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an " acousto-electrical speckle " in the Lorentz Force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging.
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Lorentz Force electrical impedance tomography
arXiv: Medical Physics, 2014Co-Authors: Pol Graslandmongrain, Jean-yves Chapelon, Jean Martial Mari, Cyril LafonAbstract:This article describes a method called Lorentz Force Electrical Impedance Tomography. The electrical conductivity of biological tissues can be measured through their sonication in a magnetic field: the vibration of the tissues inside the field induces an electrical current by Lorentz Force. This current, detected by electrodes placed around the sample, is proportional to the ultrasonic pressure, to the strength of the magnetic field and to the electrical conductivity gradient along the acoustic axis. By focusing at different places inside the sample, a map of the electrical conductivity gradient can be established. In this study experiments were conducted on a gelatin phantom and on a beef sample, successively placed in a 300 mT magnetic field and sonicated with an ultrasonic transducer focused at 21 cm emitting 500 kHz bursts. Although all interfaces are not visible, in this exploratory study a good correlation is observed between the electrical conductivity image and the ultrasonic image. This method offers an alternative to detecting pathologies invisible to standard ultrasonography.
Guy Cloutier - One of the best experts on this subject based on the ideXlab platform.
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Acousto-electrical speckle pattern in Lorentz Force electrical impedance tomography
Physics in Medicine and Biology, 2015Co-Authors: Pol Grasland-mongrain, José María Navarro Marí, Stefan Catheline, Francois Destrempes, Jean-yves Chapelon, Remi Souchon, Cyril Lafon, Guy CloutierAbstract:Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz Force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz Force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz Force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz Force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an " acousto-electrical speckle " in the Lorentz Force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging.
