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A 3-Axis Miniature Magnetic Sensor Based on a Planar Fluxgate Magnetometer with an Orthogonal Fluxguide.

Lu CC, Huang J - Sensors (Basel) (2015)

Bottom Line: Experimental characterization of the miniature fluxgate device demonstrates satisfactory spatial magnetic field detection results in terms of responsivity and noise spectrum.As a result, at an excitation frequency of 50 kHz, a maximum in-plane responsivity of 122.4 V/T appears and a maximum out-of-plane responsivity of 11.6 V/T is obtained as well.The minimum field noise spectra are found to be 0.11 nT/√Hz and 6.29 nT/√Hz, respectively, in X- and Z-axis at 1 Hz under the same excitation frequency.

View Article: PubMed Central - PubMed

Affiliation: Institute of Mechatronic Engineering, National Taipei University of Technology, Taipei 106, Taiwan. cclu23@ntut.edu.tw.

ABSTRACT
A new class of tri-axial miniature magnetometer consisting of a planar fluxgate structure with an orthogonal ferromagnetic fluxguide centrally situated over the magnetic cores is presented. The magnetic sensor possesses a cruciform ferromagnetic core placed diagonally upon the square excitation coil under which two pairs of pick-up coils for in-plane field detection are allocated. Effective principles and analysis of the magnetometer for 3-D field vectors are described and verified by numerically electromagnetic simulation for the excitation and magnetization of the ferromagnetic cores. The sensor is operated by applying the second-harmonic detection technique that can verify V-B relationship and device responsivity. Experimental characterization of the miniature fluxgate device demonstrates satisfactory spatial magnetic field detection results in terms of responsivity and noise spectrum. As a result, at an excitation frequency of 50 kHz, a maximum in-plane responsivity of 122.4 V/T appears and a maximum out-of-plane responsivity of 11.6 V/T is obtained as well. The minimum field noise spectra are found to be 0.11 nT/√Hz and 6.29 nT/√Hz, respectively, in X- and Z-axis at 1 Hz under the same excitation frequency. Compared with the previous tri-axis fluxgate devices, this planar magnetic sensor with an orthogonal fluxguide provides beneficial enhancement in both sensory functionality and manufacturing simplicity. More importantly, this novel device concept is considered highly suitable for the extension to a silicon sensor made by the current CMOS-MEMS technologies, thus emphasizing its emerging applications of field detection in portable industrial electronics.

No MeSH data available.


A 3-D model of a planar excitation coils and its simulated result with a 2-mm cruciform ferromagnetic core under the excitation current of 5 A.
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sensors-15-14727-f006: A 3-D model of a planar excitation coils and its simulated result with a 2-mm cruciform ferromagnetic core under the excitation current of 5 A.

Mentions: Afterward, a 3-D model example of the planar excitation coils with a 2-mm cruciform ferromagnetic core, as shown in Figure 6, is accordingly built and analyzed. For electromagnetic excitation and core magnetization, an excitation current of 0.5 A and the B-H loop data of the core material are employed, and it is found that the excitation coils are easily able to achieve the magnetic saturation of the core employed (>10 µT). Again the location of maximum flux density is approximately close to the middle position of the half-core in X- or Y-sensing orientation, which is feasible for in-plane detection. In addition, to measure the orthogonal Z-axis fields, another ultimate design including the planar excitation coils with a cruciform core and a ferrite fluxguide tube, as given in Figure 7, is then analyzed under a 40 A/m magnetic field along Z-axis. One can observe that a linear distribution of magnetic flux density in the core rises from the inner diameter (i.e., ±4.5 mm) to the outer diameter (i.e., ±8 mm) and reaches the maximum value of 0.56 T, yet, beyond that point, the magnetic flux density is linearly decreased to zero with the increased longitudinal distance till the end of the core. The orthogonal flux vectors guided into the in-plane core, even though not all of them, can be easily measured by switching to the Z-axis sensing mode. According to the simulated result, it is also promising to elevate the variation of magnetic flux density, i.e., the responsivity, within the sensing area of a pick-up coils simply by placing a larger cylindrical fluxguide tube close to the end of the core. From the manufacturing point of view, the proposed simple structure is particularly considered superior to those complicated 3-D devices using traditionally monolithic or assembly methods employed before.


A 3-Axis Miniature Magnetic Sensor Based on a Planar Fluxgate Magnetometer with an Orthogonal Fluxguide.

Lu CC, Huang J - Sensors (Basel) (2015)

A 3-D model of a planar excitation coils and its simulated result with a 2-mm cruciform ferromagnetic core under the excitation current of 5 A.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507702&req=5

sensors-15-14727-f006: A 3-D model of a planar excitation coils and its simulated result with a 2-mm cruciform ferromagnetic core under the excitation current of 5 A.
Mentions: Afterward, a 3-D model example of the planar excitation coils with a 2-mm cruciform ferromagnetic core, as shown in Figure 6, is accordingly built and analyzed. For electromagnetic excitation and core magnetization, an excitation current of 0.5 A and the B-H loop data of the core material are employed, and it is found that the excitation coils are easily able to achieve the magnetic saturation of the core employed (>10 µT). Again the location of maximum flux density is approximately close to the middle position of the half-core in X- or Y-sensing orientation, which is feasible for in-plane detection. In addition, to measure the orthogonal Z-axis fields, another ultimate design including the planar excitation coils with a cruciform core and a ferrite fluxguide tube, as given in Figure 7, is then analyzed under a 40 A/m magnetic field along Z-axis. One can observe that a linear distribution of magnetic flux density in the core rises from the inner diameter (i.e., ±4.5 mm) to the outer diameter (i.e., ±8 mm) and reaches the maximum value of 0.56 T, yet, beyond that point, the magnetic flux density is linearly decreased to zero with the increased longitudinal distance till the end of the core. The orthogonal flux vectors guided into the in-plane core, even though not all of them, can be easily measured by switching to the Z-axis sensing mode. According to the simulated result, it is also promising to elevate the variation of magnetic flux density, i.e., the responsivity, within the sensing area of a pick-up coils simply by placing a larger cylindrical fluxguide tube close to the end of the core. From the manufacturing point of view, the proposed simple structure is particularly considered superior to those complicated 3-D devices using traditionally monolithic or assembly methods employed before.

Bottom Line: Experimental characterization of the miniature fluxgate device demonstrates satisfactory spatial magnetic field detection results in terms of responsivity and noise spectrum.As a result, at an excitation frequency of 50 kHz, a maximum in-plane responsivity of 122.4 V/T appears and a maximum out-of-plane responsivity of 11.6 V/T is obtained as well.The minimum field noise spectra are found to be 0.11 nT/√Hz and 6.29 nT/√Hz, respectively, in X- and Z-axis at 1 Hz under the same excitation frequency.

View Article: PubMed Central - PubMed

Affiliation: Institute of Mechatronic Engineering, National Taipei University of Technology, Taipei 106, Taiwan. cclu23@ntut.edu.tw.

ABSTRACT
A new class of tri-axial miniature magnetometer consisting of a planar fluxgate structure with an orthogonal ferromagnetic fluxguide centrally situated over the magnetic cores is presented. The magnetic sensor possesses a cruciform ferromagnetic core placed diagonally upon the square excitation coil under which two pairs of pick-up coils for in-plane field detection are allocated. Effective principles and analysis of the magnetometer for 3-D field vectors are described and verified by numerically electromagnetic simulation for the excitation and magnetization of the ferromagnetic cores. The sensor is operated by applying the second-harmonic detection technique that can verify V-B relationship and device responsivity. Experimental characterization of the miniature fluxgate device demonstrates satisfactory spatial magnetic field detection results in terms of responsivity and noise spectrum. As a result, at an excitation frequency of 50 kHz, a maximum in-plane responsivity of 122.4 V/T appears and a maximum out-of-plane responsivity of 11.6 V/T is obtained as well. The minimum field noise spectra are found to be 0.11 nT/√Hz and 6.29 nT/√Hz, respectively, in X- and Z-axis at 1 Hz under the same excitation frequency. Compared with the previous tri-axis fluxgate devices, this planar magnetic sensor with an orthogonal fluxguide provides beneficial enhancement in both sensory functionality and manufacturing simplicity. More importantly, this novel device concept is considered highly suitable for the extension to a silicon sensor made by the current CMOS-MEMS technologies, thus emphasizing its emerging applications of field detection in portable industrial electronics.

No MeSH data available.