穿隧式接面薄膜於磁場感測影像系統之開發與研究

Abstract

量測未爆彈常用系統TEM(Time domain electromagnetics)，其體積由於過大所以量測便利性不高，本實驗藉由TMR之特性設計一系統，並嘗試改進TEM系統之缺陷。本實驗於電磁波屏蔽室內進行實驗，量測調製線圈磁場以及電流之關係，並接續量測TMR電壓對應不同磁場之關係，用以得到磁場大小，便接續探討TMR驅動呈現性特性所需之調製場，尋找最低驅動條件來驅動TMR，使其運作，量測方式則是採用被動方式偵測鐵磁性物質，並無給予激發場。在訊號端，藉由Filter將激發頻率濾除，並以DAQ接收MTJ訊號。掃描端則使用三維步進馬達來移動樣品進行掃描，以取得訊號源分布圖，並帶入實驗數據，使用模擬軟體進行演算，最後用線性擬合的方式進行數據比對。感測器本身輸出數值為電壓，所以藉由得到線圈電流磁場轉換比0.49162 mT/A並在得到感測器電壓磁場轉換比3.00311 V/mT，即可得到電壓轉換磁場數值，在這之後，藉由掃描背景雜訊數值得到靈敏度為〖10〗^(-5) mT以及背景雜訊最大值最小值差異為2.06E-04 mT，以此為標準，再量測1.4177 mT、彈徑105 mm的未爆彈情況下可深達1.1 m，並從量測待測物偶極矩比對模擬偶極矩數值來看，相差了大約1.5倍左右，但此結果來看是合理的，由於待測偶極矩為一具有體積之物體，所以大於模擬為正常，而結論而言，此系統具有一定程度之發展性。

TEM (Time domain electromagnetics), a commonly used system for measuring unexploded bombs, is not convenient for measurement due to its large size. This experiment designed a system based on the characteristics of TMR, and tried to improve the defects of the TEM system.This experiment is carried out in an electromagnetic wave shielding room to measure the relationship between the magnetic field of the modulation coil and the current, and then to measure the relationship between the TMR voltage and different magnetic fields to obtain the magnitude of the magnetic field, and then continue to discuss the modulation field required for the performance characteristics of the TMR drive. , looking for the lowest driving conditions to drive the TMR to make it work, and the measurement method is to use a passive method to detect ferromagnetic substances without giving an excitation field. On the signal side, use Filter to filter out the excitation frequency, and use DAQ to receive the MTJ signal. The scanning end uses a three-dimensional stepping motor to move the sample for scanning to obtain the distribution map of the signal source, and bring in the experimental data, use the simulation software for calculation, and finally use the linear fitting method for data comparison.The output value of the sensor itself is voltage, so by obtaining the coil current magnetic field conversion ratio of 0.49162 mT/A and the sensor voltage magnetic field conversion ratio of 3.00311 V/mT, the voltage converted magnetic field value can be obtained. After that, borrow By scanning the background noise value, the sensitivity is 10^(-5) mT and the difference between the maximum value and the minimum value of the background noise is 2.06E-04 mT. Using this as a standard, measure 1.4177 mT and a bullet diameter of 105 mm It can be as deep as 1.1 m in the case of unexploded bombs,And from the measurement of the dipole moment of the object to be measured compared to the value of the simulated dipole moment, the difference is about 1.5 times, but this result is reasonable, because the dipole moment to be measured is an object with a volume, so It is normal to be larger than the simulation, and in conclusion, this system has a certain degree of development.