異向性磁敏電阻高低頻雜訊解決方案研究;High and low frequency noise solutions of anisotropic magnetic resistance sensors

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题名:	異向性磁敏電阻高低頻雜訊解決方案研究;High and low frequency noise solutions of anisotropic magnetic resistance sensors
作者:	王長盛;Wang,Chang Sheng
贡献者:	光機電工程研究所
关键词:	磁敏電阻;地磁感測;磁力;AMR;Magnetic
日期:	2015-08-19
上传时间:	2015-09-23 11:19:37 (UTC+8)
出版者:	國立中央大學
摘要:	本研究以提高磁場感測精度並擴大磁場量測範圍為目的，克服異向性磁敏電阻感測器周邊低頻殘磁以及高頻數位電路雜訊之干擾，以提高精度並擴增量測範圍。本研究利用自適應偏磁場補償，抵消周邊強殘磁，使感測器感測磁場落在感測曲線最敏感之線性區域內，一方面提高磁感測範圍，另一方面維持高敏感度。本研究以超取樣技術得以施行並濾除電路高頻干擾雜訊，提高量測解析度；而為滿足其適用的訊號平滑條件，本研究必須採取取樣保值避開SET/RESET當時的強磁干擾、翻轉惠斯登電橋電流方向克服SET/RESET後量測訊號的反向、等措施，才得使AMR的輸出訊號維持均值平滑。本研究以取樣保值避開SET/RESET當時的強磁干擾，以翻轉惠斯登電橋電流方向克服SET/RESET後量測訊號的反向，讓AMR輸出訊號維持均值平衡，使超取樣技術得以施行並濾除電路高頻干擾雜訊，提高量測解析度。本研究開發完成提升精密度之電路之外，並以亥姆霍茲線圈提供可控磁場，實際量測驗證新設計電路之量測範圍，以及量測精度，驗證研究目標的達成。經過實測，SET/RESET前後的訊號保持及翻轉電橋電流源方向可以將訊號跳動降到2uV以下,相當於15bit的精度。經過校正之後，本磁力計的量測精度在1440倍超頻採樣下，可達20nTesla。HMC1001/1002感測元件的電流補償可以有效產生±1Gauss的磁場補償作用。;To improve the dynamic precision and the dynamic range of the anisotropic magnetic resistance sensors, it is necessary to compensate the inherent environmental magnetic field offset and to filter out random variations. Field compensation current can be applied to the AMR sensors adaptively to cancel the slowly varying environmental magnetic field offset so that the residual dynamics fall in the linear and most sensitive range of the sensors that can be measured with high resolution and precision through out a wide range of total field strength. Fast data over-sampling by sigma-delta algorithm can be applied to filter random variations so as to improve the precision to measure smooth signals. Therefore, S/H is used to block the pulses of the SET/RESET on the AMR from its signal to data sampling. The driving current to its sensing bridge should also be reversed from the set phase to the reset phase to avoid signal jump due to sign change of the differential signal. The blocking by S/H and the synchronous direction change of the sensor driving current reduces the signal jitter to lower than 2uV which is a precision improvement down to 15bits of the data sampling. After calibration the improved AMR yields a measurement with the precision of 20nTesla. The current compensation in the HMC1001/1002 sensors may compensate persistent magnetic background upto ±1Gauss.
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