Orthogonal Fluxgate With Annealed Wire Core
Orthogonal Fluxgate With Annealed Wire Core
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DOI：
10.1109/tmag.2012.2218094
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发表时间：
2013-01-01
影响因子：
2.1
通讯作者：
Sasada, Ichiro
中科院分区：
文献类型：
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作者：
Butta, Mattia;Sasada, Ichiro
基模正交磁通门已成为低频磁场低噪声测量的一种极具竞争力的传感器。该传感器在1赫兹时的噪声已降至2.8pT/根赫兹；但是，由于磁通门铁心产生的固有噪声的物理限制，在1赫兹时似乎无法实现低于2.5pT/根赫兹的噪声。为了在1赫兹时将噪声降低到2.5pT/根赫兹以下，必须降低铁芯中产生的巴克豪森噪声。为此，我们在红外炉中对用作传感器核心的非晶丝进行了退火处理，同时直流电流流过该丝。直流电流产生了一个足够大的圆周磁场，使导线在圆周方向上饱和，通过对饱和的导线进行热处理，我们增加了圆周各向异性。我们说明了周向各向异性与导线中的直流电流以及退火温度和时间的关系。然后，我们证明了当磁通门工作在基模时，较大的周向各向异性有助于降低传感器的噪声，从而抑制巴克豪森噪声。结果是，使用退火线可获得1.8pT/根赫兹的噪声，远低于使用铸态线的传感器所能达到的2.5pT/根赫兹的最小噪声。
Orthogonal fluxgate in fundamental mode has become a competitive sensor for low noise measurement of low frequency magnetic fields. The noise of this sensor has been recently reduced to 2.8 pT/root Hz at 1 Hz; however, it appears that noise lower than 2.5 pT/root Hz at 1 Hz cannot be achieved because of the physical limitations due to the intrinsic noise generated in the core of the fluxgate. In order to decrease the noise below 2.5 pT/root Hz at 1 Hz, Barkhausen noise generated in the core must be reduced. For this purpose, we annealed the amorphous wire used as the core of the sensor in an infrared furnace while a dc current was flowing through the wire. The dc current generated a circumferential field large enough to saturate the wire in a circumferential direction, and by annealing the saturated wire, we increased the circumferential anisotropy. We illustrate the dependence of circumferential anisotropy on dc current in the wire as well as on temperature and time of annealing. We then demonstrate that larger circumferential anisotropy helps reduce the noise of the sensor suppressing the Barkhausen noise when the fluxgate is operated in fundamental mode. As a result, a 1.8 pT/root Hz noise at 1 Hz was achieved with annealed wire, which is far below the 2.5 pT/root Hz minimum noise achievable for sensors with as-cast wires.