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20 pages, 10234 KiB

Open AccessArticle

A Wireless Passive Pressure-Sensing Method for Cryogenic Applications Using Magnetoresistors

by Ziqi Zhao, Michitaka Yamamoto, Seiichi Takamatsu and Toshihiro Itoh

Sensors 2024, 24(3), 717; https://doi.org/10.3390/s24030717 - 23 Jan 2024

Cited by 1 | Viewed by 2191

In this study, we developed a novel wireless, passive pressure-sensing method functional at cryogenic temperatures (−196 °C). The currently used pressure sensors are inconvenient and complicated in cryogenic environments for their weak low-temperature tolerances and long wires for power supply and data transmission. We propose a novel pressure-sensing method for cryogenic applications by only using low-temperature-tolerant passive devices. By innovatively integrating a magnetoresistor (MR) on a backscattering antenna, the pressure inside a cryogenic environment is transferred to a wirelessly obtainable return loss. Wireless passive measurement is thus achieved using a backscattering method. In the measurement, the pressure causes a relative displacement between the MR and a magnet. The MR’s resistance changes with the varied magnetic field, thus modulating the antenna’s return loss. The experimental results indicate that our fabricated sensor successfully identified different pressures, with high sensitivities of 4.3 dB/MPa at room temperature (24 °C) and 1.3 dB/MPa at cryogenic temperature (−196 °C). Additionally, our method allows for simultaneous wireless readings of multi sensors via a single reading device by separating the frequency band of each sensor. Our method performs low-cost, simple, robust, passive, and wireless pressure measurement at −196 °C; thus, it is desirable for cryogenic applications. Full article

(This article belongs to the Special Issue RFID and Zero-Power Backscatter Sensors)

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16 pages, 2361 KiB

Open AccessArticle

A Non-Inductive Magnetic Eye-Tracker: From Dipole Tracking to Gaze Retrieval

by Valerio Biancalana and Piero Chessa

Instruments 2023, 7(1), 8; https://doi.org/10.3390/instruments7010008 - 7 Feb 2023

Cited by 3 | Viewed by 2571

Abstract

We analyze the information that can be retrieved from the tracking parameters produced by an innovative wearable eye tracker. The latter is based on a permanent-magnet marked corneal lens and by an array of magnetoresistive detectors that measure the magnetostatic field in several positions in the eye proximity. We demonstrate that, despite missing information due to the axial symmetry of the measured field, physiological constraints or measurement conditions make possible to infer complete eye-pose data. Angular precision and accuracy achieved with the current prototypical device are also assessed and briefly discussed. The results show that the instrumentation considered is suitable as a new, moderately invasive medical diagnostics for the characterization of ocular movements and associated disorders. Full article

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15 pages, 10418 KiB

Open AccessEditor’s ChoiceArticle

Validation of a Fast and Accurate Magnetic Tracker Operating in the Environmental Field

by Valerio Biancalana, Roberto Cecchi, Piero Chessa, Marco Mandalà, Giuseppe Bevilacqua, Yordanka Dancheva and Antonio Vigilante

Instruments 2021, 5(1), 11; https://doi.org/10.3390/instruments5010011 - 5 Mar 2021

Cited by 8 | Viewed by 3555

Abstract

We characterize the performance of a system based on a magnetoresistor array. This instrument is developed to map the magnetic field, and to track a dipolar magnetic source in the presence of a static homogeneous field. The position and orientation of the magnetic source with respect to the sensor frame is retrieved together with the orientation of the frame with respect to the environmental field. A nonlinear best-fit procedure is used, and its precision, time performance, and reliability are analyzed. This analysis is performed in view of the practical application for which the system is designed that is an eye-tracking diagnostics and rehabilitative tool for medical purposes, which require high speed (≥100 Sa/s) and sub-millimetric spatial resolution. A throughout investigation on the results makes it possible to list several observations, suggestions, and hints, which will be useful in the design of similar setups. Full article

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17 pages, 1630 KiB

Open AccessArticle

Fast, Cheap, and Scalable Magnetic Tracker with an Array of Magnetoresistors

by Valerio Biancalana, Roberto Cecchi, Piero Chessa, Giuseppe Bevilacqua, Yordanka Dancheva and Antonio Vigilante

Instruments 2021, 5(1), 3; https://doi.org/10.3390/instruments5010003 - 28 Dec 2020

Cited by 8 | Viewed by 3896

Abstract

We present the hardware of a cheap multi-sensor magnetometric setup, where a relatively large set of magnetic field components is measured in several positions by calibrated magnetoresistive detectors. The setup is developed to map the (inhomogeneous) field generated by a known magnetic source, which is measured and then discerned from the background (homogeneous) geomagnetic field. The data output from this hardware can be successfully and reliably used to retrieve the position and orientation of the magnetic source with respect to the sensor frame, together with the orientation of the frame with respect to the environmental field. Possible applications of the setup are briefly discussed, and a synthetic description of the methods of data elaboration and analysis is provided. Full article

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24 pages, 4241 KiB

Open AccessEditor’s ChoiceReview

Magnetorheological Elastomers: Fabrication, Characteristics, and Applications

by Sung Soon Kang, Kisuk Choi, Jae-Do Nam and Hyoung Jin Choi

Materials 2020, 13(20), 4597; https://doi.org/10.3390/ma13204597 - 15 Oct 2020

Cited by 105 | Viewed by 11010

Abstract

Magnetorheological (MR) elastomers become one of the most powerful smart and advanced materials that can be tuned reversibly, finely, and quickly in terms of their mechanical and viscoelastic properties by an input magnetic field. They are composite materials in which magnetizable particles are dispersed in solid base elastomers. Their distinctive behaviors are relying on the type and size of dispersed magnetic particles, the type of elastomer matrix, and the type of non-magnetic fillers such as plasticizer, carbon black, and crosslink agent. With these controllable characteristics, they can be applied to various applications such as vibration absorber, isolator, magnetoresistor, and electromagnetic wave absorption. This review provides a summary of the fabrication, properties, and applications of MR elastomers made of various elastomeric materials. Full article

(This article belongs to the Special Issue Advances in Elastomers)

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4 pages, 276 KiB

Open AccessProceeding Paper

In-Plane Sensitive Magnetoresistors as a Hall Device

by Siya Lozanova, Ivan Kolev, Avgust Ivanov and Chavdar Roumenin

Proceedings 2018, 2(13), 710; https://doi.org/10.3390/proceedings2130710 - 5 Dec 2018

Viewed by 1501

Abstract

A novel coupling of a pair of identical two-contact (2C) magnetoresistors transformed into an in-plane sensitive Hall device is presented. The ohmic contacts are cross-linked, also adding a load resistor bridge, providing for constant current mode of operation and eliminating the inevitable parasitic offset. This silicon configuration, apart from its simplified layout, has linear and odd output voltage as a function of the magnetic field and current. The quadratic and even magnetoresistance in the two parts of this innovative device is completely compensated, which ensures high measurement accuracy alongside with identification of the magnetic field polarity. The experimental prototypes feature sensitivity of 110 V/AT. The mean lowest detected magnetic induction B at supply current of 3 mA over frequency range f ≤ 100 Hz at a signal-to-noise ratio equal to unity is Bmin ≈ 10 μT. Тhe high performance and the complete electrical, temperature and technological matching of the parts of this unusual Hall device make it very promising for many practical applications. Full article

(This article belongs to the Proceedings of EUROSENSORS 2018)

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