磁阻抗效應非接觸式應變計之研究

傳統量測系統使用的電阻式應變計，大都採用黏貼於材料或機台表面，為接觸式量測，然而量測靈敏度較低，需要外加高倍率訊號放大電路，在環境惡劣之場合使用，較容易受到干擾，雜訊容忍度較低。磁阻抗效應傳感器技術，採用非接觸式應變量測原理，具有量測靈敏度較高之優點。磁阻抗效應傳感器在以往的應用上，使用螺旋繞線線圈搭配外部的激磁訊號源，再利用頻率偵錯或相位偵測，在這樣的架構下的量測電路缺點有，線圈體積較為龐大，需要穩定之外接訊號源，頻譜轉換需要較為昂貴之量測儀器等，有鑑於此，本研究提出新型磁阻抗效應非接觸式應變感測器。本文研究之磁阻抗效應非接觸式應變感測器，材料選用非晶態軟磁材料Metglas 2826MB，訊號處理電路使用考畢子諧振(Colpitts oscillator)電路，並結合平面線圈(planar spiral coil)，對非晶態薄膜進行激磁，在非晶態薄膜表面產生渦電流(eddy current)效應，此效應會使得非晶態薄膜，反饋阻抗變化給平面線圈；當非晶態薄膜受外力產生變形時，會使得量測電路與非晶態材料互感的導磁率及導電率產生改變，平面線圈阻抗隨之產生變化，其諧振訊號振幅值產生改變，經由均方根值電路(True-RMS circuit)輸出應變量對應的類比電壓值，並與傳統應變計做一比較。另外，本研究針對旋轉軸應變計部分，亦完成旋轉軸型式巨磁阻抗(GMI)應變量測電路之雛型設計，在材料上採用CoFeSiB非晶態微細線(micro wire)，並改變平面線圈構型，採用兩個圓型中空平面線圈耦合方式，進行應變量測與驗證。經由實驗結果顯示，本研究開發的非接觸式應變感測器，在阻抗分析上，100Hz~30MHz的掃頻範圍下，平面線圈圈數越多，在施加相同應力下，量測的阻抗變化越大，矩型平面線圈圈數在16匝，線圈面積為16.3 mm，線圈激磁訊號為24.5MHz時，非晶態薄膜尺寸20mm×7mm×28μm，其量測靈敏度為7.24 mV/με；而旋轉型巨磁阻抗應變感測器，在CoFeSiB微細線長度為8mm，線徑為30μm，耦合線圈激磁訊號為1.5MHz時，在初步完成的靜態測試下，其量測靈敏度可達到11.7 mV/με。在直流偏磁實驗上，施加直流偏磁場平行於施力方向，直流偏磁場低於0.08mT，量測靈敏度不會受到此直流偏磁場之影響，且直流偏磁場在0.04mT時，量測靈敏度會提高到10.0 mV/με。本研究所開發的「磁阻抗效應非接觸式應變感測器」，改善了以往使用螺旋繞線線圈體積較為龐大之問題，在量測電路上，也無需外部激磁之訊號產生器，與昂貴的量測儀器，減少實際使用時需要之儀器設備，更重要的是本研究電路架構簡單，平面線圈在製造上容易且價格便宜，平面線圈特性均質性高，並且量測靈敏度高，在其功能性上相比，較以前使用之電路架構更貼合實際應用時之需求。

關鍵字

非晶態磁性材料；磁阻抗效應；應變計；考畢子諧振電路

並列摘要

Based on the magnetoelastic effect, this study develops a non-contact strain sensor consisting of a magnetoelastic film by using low-priced and highly-sensitive Metglas 2826MB amorphous ribbons as the strain measure material. Furthermore, a planar spiral coil combined in a Colpitts oscillator circuit is used to excite the magnetoelastic film. Under a tensile load, a mechanical deformation of the amorphous ribbons occurs and alters its permeability and conductivity. This results in a variation of impedance on the film coupled with the planar spiral coil as well as in the corresponding voltage output to be measured. In addition, the study of the non-contact torque sensor in the giant magneto-impedance (GMI) effect base on amorphous micro wire has been conducted. The GMI strain sensor for torque measurement also can be applied to the rotation axis. The torque sensor materials used CoFeSiB amorphous micro wire, and used two circular hollow planar coil couplings for strain measurement and verification. The experimental results show that the measurement sensitivity can reach a sensitivity 7.24 mV/με of the non-contact strain sensor, a non-linearity of 4.4%, and a hysteresis of 3.6%. Moreover, measurement sensitivity can reach 11.7 mV/με of the torque sensor in GMI wire prototype. Instead of using a conventional coil wound around a bar in most of the other related works, the coil used for this designed sensor is of planar form which offers the advantages of a simplified manufacturing process, uniformity in coil characteristics, compactness, and low manufacturing cost. The circuit architecture for the proposed sensor is rather simple and low-priced compared with that of the widely-used frequency-domain system, requiring a function generator to generate a fixed-frequency steady state signal to excite the coil, and the received sensor response is sent to a lock-in amplifier to be amplified and measured. The advantages are a simplified manufacturing process, uniformity in coil characteristics, compactness, uncomplicated circuit architecture, and low manufacturing cost. Moreover, a promising potential for further improvement makes the designed sensor suitable for future practical applications.

並列關鍵字

giant magneto-impedance effect ； Colpitts oscillator ； magnetoelastic effect ； planar coil

參考文獻

1.L. E. Lenz,“A review of magnetic sensors,” Proceedings of the IEEE, 1990, Vol.78, pp.973–989.

2.T. Meydan “Application of amorphous materials to sensors,” Journal of Magnetism and Magnetic HHMaterialsHH ,1995, Vol.133, pp.525–532.

3.P. Ripka “Magnetic sensors and magnetometers,” Artech House, 2001, ISBN 1580530575.

4.L. V. Panina and K. Mohri, “Magnetoimpedance effect in amorphous wires, ” American Institute of Physics, 1994, Vol.65, pp.1189-1191.

5.K. Mohri and E. Sudoh, “Sensitive force transducers using a single amorphous core multivibrator bridge, ” IEEE Transactions on magnetics, Vol.15, NO.6, 1979, pp.1806-1808

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磁阻抗效應非接觸式應變計之研究

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