Calibration of Room Temperature Magnetic Sensor Array for Biomagnetic Measurement

Adachi, Yoshiaki; Oyama, Daisuke; Terazono, Yasushi; Hayashi, Tatsuya; Shibuya, Tadaharu; Kawabata, Shigenori

doi:10.1109/tmag.2019.2895355

Cited by 26 publications

(16 citation statements)

References 8 publications

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“…3 for the following reason. When we calibrated the sensor array composed of the same MR-based sensors using a set of calibration coils arranged relatively away from the sensor array [11], assuming the sensing area as a single point, the sensing point of each sensor was localized approximately 15 mm away from the one end of the sensor module package. Assuming that the flux concentrator had a symmetric structure, the sensing point should be localized at the center of the flux concentrator.…”

Section: B Multiple Sensitivity Points Model and Calibrationmentioning

confidence: 99%

Evaluation of Directional Dependence of Sensitivity for Room-Temperature Magnetic Flux Sensors With Wide Sensitivity Region

2021

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Recently, the room-temperature (RT) magnetic flux sensors are becoming used for biomagnetic measurements. The RT sensors have a large advantage that they can be placed closer to the magnetic sources and obtain larger signals, unlike the superconducting quantum interference device (SQUID) flux sensors. However, when an RT sensor is placed closer to the sources, the dimension of the sensitivity region cannot be negligible, and the directional dependence of sensitivity should be considered to estimate the theoretical magnetic signals for magnetic source analysis. We proposed a method to evaluate the directional dependence of the sensitivity of the RT sensors in response to adjacent magnetic sources using the array of coils arranged along a circular arc. Consequently, it was revealed that a specific magnetoresistance device-based flux sensor with a certain spatial extent had the directional dependence of sensitivity with a bell-shaped profile. We also proposed the multiple sensitivity points model for the bell-shaped profile and estimated the sensitivity distribution over the sensitivity region, which is expected to be effective in improving the accuracy of the magnetic source analysis using an RT sensor array.

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Section: B Multiple Sensitivity Points Model and Calibrationmentioning

confidence: 99%

Evaluation of Directional Dependence of Sensitivity for Room-Temperature Magnetic Flux Sensors With Wide Sensitivity Region

2021

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“…K. Fujiwara et al improved the signal-to-noise ratio of the TMR sensor and successfully measured MCG signals [19]. A calibration method using multiple coils was proposed in [20], which was applied to a TMR-based MCG system equipped with a planar sensor array. The calibration considerably improved the accuracy of the magnetic source analysis, and a preliminary MCG measurement using the calibrated magnetic sensor array was presented.…”

Section: Introductionmentioning

confidence: 99%

Tunnel Magnetoresistance Sensor with AC Modulation and Impedance Compensation for Ultra-Weak Magnetic Field Measurement

Zhao

Tao

et al. 2022

Sensors

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Tunnel magnetoresistance (TMR) is a kind of magnetic sensor with the advantages of low cost and high sensitivity. For ultra-weak and low-frequency magnetic field measurement, the TMR sensor is affected by the 1/f noise. This paper proposes an AC modulation method with impedance compensation to improve the performance. The DC and AC characteristics of the sensors were measured and are presented here. It was found that both the equivalent resistance and capacitor of the sensors are affected by the external magnetic field. The TMR sensors are connected as a push–pull bridge circuit to measure the magnetic field. To reduce the common-mode noise, two similar bridge circuits form a magnetic gradiometer. Experimental results show that the sensor’s sensitivity in the low-frequency range is obviously improved by the modulation and impedance compensation. The signal-to-noise ratio of the sensor at 1 Hz was increased about 25.3 dB by the AC modulation, impedance compensation, and gradiometer measurement setup. In addition, the sensitivity of the sensor was improved from 165.2 to 222.1 mV/V/mT. Ultra-weak magnetic signals, namely magnetocardiography signals of two human bodies, were measured by the sensor in an unshielded environment. It was seen that the R peak of MCG can be clearly visualized from the recorded signal.

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“…As a result, their spatial resolution and the number of sensing elements are limited by the sensor size and the number of wires. [6][7][8] The electromagnetic field imaging using NV centers in diamond is free from this limitation because acquisition of an image is performed all optically by collecting the PL from NV centers. Furthermore, quantum sensing techniques enable high precision and sensitivity of electromagnetic field detection.…”

Section: Introductionmentioning

confidence: 99%

Near-field radio-frequency imaging by spin-locking with a nitrogen-vacancy spin sensor

Nomura

Kaida

Watanabe

et al. 2021

Journal of Applied Physics

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We present results of near-field radio-frequency (RF) imaging at micrometer resolution using an ensemble of nitrogen-vacancy (NV) centers in diamond. The spatial resolution of RF imaging is set by the resolution of an optical microscope, which is markedly higher than the existing RF imaging methods. High sensitivity RF field detection is demonstrated through spin locking. SCROFULOUS composite pulse sequence is used for manipulation of the spins in the NV centers for reduced sensitivity to possible microwave pulse amplitude error in the field of view. We present procedures for acquiring an RF field image under spatially inhomogeneous microwave field distribution, and demonstrate a near-field RF imaging of an RF field emitted from a photolithographically defined metal wire. The obtained RF field image indicates that the RF field intensity has maxima in the vicinity of the edges of the wire, in accord with a calculated result by a finite-di↵erence time-domain method. Our method is expected to be applied in a broad variety of application areas, such as material characterizations, characterization of RF devices, and medical fields.

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Calibration of Room Temperature Magnetic Sensor Array for Biomagnetic Measurement

Cited by 26 publications

References 8 publications

Evaluation of Directional Dependence of Sensitivity for Room-Temperature Magnetic Flux Sensors With Wide Sensitivity Region

Evaluation of Directional Dependence of Sensitivity for Room-Temperature Magnetic Flux Sensors With Wide Sensitivity Region

Tunnel Magnetoresistance Sensor with AC Modulation and Impedance Compensation for Ultra-Weak Magnetic Field Measurement

Near-field radio-frequency imaging by spin-locking with a nitrogen-vacancy spin sensor

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