Fe3O4纳米颗粒-SU8胶材料的电磁特性研究

近年来铁磁性Fe3O4纳米颗粒以其良好的导磁特性、超顺磁效应、磁光效应和磁热效应等越来越受到重视。以Fe3O4纳米颗粒和聚合物SU8胶为原料,制备了一种可用于磁场检测的颗粒薄膜材料,并对其磁场响应作了测试。该颗粒膜介电特性随着磁场强度的增加而减小,利用其电容特性来检测磁场的变化,可以作为一种新型的磁传感器材料,应用广泛。     

InSb磁敏电阻角位移传感器的研究

简单分析了InSb磁敏电阻的工作原理,讨论了利用偏置磁场作用于半桥磁敏电阻构成转动速度及位移传感器的测试原理;针对半导体材料对温度十分敏感的特点,提出了利用浮动零点跟踪技术测试齿轮转速的方法,并对其优缺点进行了讨论。     

用于心磁传感器测试系统的三轴向亥姆赫兹线圈的设计与仿真

心磁检测对于心脏相关疾病的诊断具有独特优势，在用于测量心脏磁场的传感器(下称心磁传感器）的研制过程中，需要在模拟心磁的磁场环境下进行测试工作。基于此，设计了一个用于心磁传感器测试系统的亥姆赫兹线圈，它可以产生磁感应强度为pT级的动态磁场，模拟心磁环境，以满足心磁传感器测试的需求。根据亥姆赫兹线圈的磁场产生原理，使用磁屏蔽筒对环境磁场进行屏蔽，通过计算确定了线圈尺寸、线圈匝数、导线长度及导线横截面直径等参数。使用COMSOL Multiphysics仿真软件对亥姆赫兹线圈产生的静态磁场的分布均匀性以及通入线圈电流变化时磁场的动态特性进行仿真分析。仿真结果表明，所设计的亥姆赫兹线圈满足设计要求，能够产生磁场强度为100 pT左右、均匀度小于5%、波形实时性好的类心脏磁场波形，为心磁传感器的测试提供了良好的测试环境。所设计的亥姆赫兹线圈能够用于心磁传感器的测试工作，为心磁传感器的实际应用奠定了基础。     

基于漏磁原理的火炮零部件裂纹检测装置的设计与实现

为解决火炮零部件上裂纹等缺陷的检测问题,依据漏磁检测原理及缺陷漏磁场偶极子模型,设计了火炮零部件漏磁检测装置并进行了工程化实现.考虑到火炮零部件结构多样性,采用霍尔器件和磁阻传感器设计了多种结构的检测装置;针对漏磁信号中存在干扰信号和系统噪声的问题,采用自适应滤波和MORET-P小波变换技术,进行了信号的预处理.应用结果表明:该装置原理可行,多种结构的检测装置满足了不同火炮零部件的检测需要,自适应滤波和MORET-P小波变换技术较好地剔除了干扰信号和系统噪声,有效提取出缺陷信号.     

生物传感用巨磁电阻传感器及其磁珠检测性能

本文采用直流磁控溅射沉积了结构为NiFeCo(缓冲层)/[Cu/NiFeCo]×10/ Ta,巨磁电阻(GMR)值为9.8%的多层膜,利用微细加工技术制备了基于此GMR多层膜的生物传感器,GMR电阻线条的线宽分别为3μm和5μm.测试了单个GMR传感器的特性,并将该传感器件和外接可调电阻组成惠斯通电桥,采用该GMR电桥对Dynal公司的MyOne磁珠进行了检测.分别测试了施加变化垂直磁场和施加间歇式恒定垂直磁场时GMR电桥信号对传感器表面覆盖磁珠的响应,研究了GMR电桥信号和磁珠覆盖率的关系.选用器件电阻线宽分别为3μm和5μm的传感器测试了器件线宽对传感器灵敏度的影响.结果表明,GMR传感器能够检测到磁珠的存在,最低能检测的磁珠数量约100个,且GMR电桥信号与磁珠覆盖率基本成正比,器件的灵敏度与传感器线宽基本成反比.     

平面电容传感器热障涂层缺陷检测系统

为有效检测热障涂层的缺陷,研究基于平面电容传感器的缺陷检测系统。该文对用于热障涂层缺陷检测的平面电容传感器的工作原理进行分析,结合热障涂层的结构,利用COMSOL有限元仿真软件对传感器结构进行优化设计,设计微小电容检测电路,并通过复导纳的方法提取检测信息,搭建热障涂层缺陷检测系统,并对系统的性能进行测试。实验测试中对3种不同厚度的氧化铝陶瓷片进行复导纳的检测,通过对检测结果进行数据分析更易区分不同厚度的陶瓷片,即基于平面电容传感器的缺陷检测系统可以有效检测出热障涂层的厚度变化缺陷。     

电容式振动传感器谐波失真自检测接口ASIC设计

为实现电容式振动传感器的谐波失真测量,针对电容式振动传感器表头设计出一种开关电容型接口ASIC芯片,采用相同电极分时复用的方法,从而避免电容敏感与静电力反馈的馈通现象.对传感器敏感电容上下极板与中间质量块间的杂散电容导致的谐波失真进行了原理分析,可知传感器二次谐波与寄生电容成正比,三次谐波与寄生电容无关.提出采用电容阵列补偿、静电力平衡反馈式闭环电路结构进行传感器谐波失真抑制,并基于静电力原理提出一种新的电容式振动传感器谐波失真自检测方法,该方法无需精密振动台,仅需要低失真度电压信号源.实际测试结果显示,谐波失真检测精度可达到-83 dB.ASIC芯片采用2μm CMOS工艺流片,刻度因子为1.2 V/g（g为重力加速度,g=9.8 m/s2）,量程为±2g,噪声密度为3×10-6g/（Hz）～（1/2）,静态功耗为40 mW.测试结果证明,该电路达到高精度微加速度计系统设计要求,可以应用到地震监测、石油勘探等领域中.     

基于隧穿磁阻效应的非侵入式高灵敏度电流传感器研究

隧穿磁阻器件是新一代磁半导体传感器,其具有高灵敏度、可实现交直流混合测量的特点。该研究介绍一种基于隧穿磁阻器件的高灵敏度非侵入式表贴电流传感器设计方法。该传感器可非侵入式安装在铜排表面实现毫安级微弱电流的测量。计算毫安级电流在铜排表面产生的感应磁场大小并提出了隧穿磁阻器件的参数选型依据。进一步设计信号调理电路并提出利用分段拟合算法弥补高灵敏度隧穿磁阻器件线性范围较小的缺陷。最后,搭建测试验证平台验证传感器设计方法。结果表明,所设计的传感器可覆盖毫安至1A的测量范围,在百毫安范围内,绝对误差小于1mA,在百毫安至1A范围内,传感器的相对误差小于2%。     

采用新型读出电路的CMOS图像传感器研究

设计了一种采用新型读出电路的CMOS图像传感器,该器件电路结构简单,由四个MOS管,一个电容构成;驱动信号源少,只需两个相配合的脉冲;功耗小于0.7mW;单端输出方便模数转换的视频信号;可以实现片内差分.给出了理论分析和电路模拟仿真的结果数据及波形.采用标准1.2μm N阱DPDM CMOS工艺设计了一个256元的实验器件,像元中心距为25μm,器件尺寸大小为1mm ×11mm,并对器件进行了主要参数的测试和数据分析,验证了该器件的功能.     

新型双轴电容式微加速度传感器优化设计研究

将ＩＣ工艺与ＬＩＧＡ工艺结合，在硅基上用镍材料制作高精度电容式双轴微加速度传感器。根据力学原理并结合所采用的工艺特点，对该器件结构进行优化设计，获得了较好的器件性能参数。结果表明，器件的静态电容为２．６ｐＦ，量程达±５ｇ。该加速度传感器可同时测量Ｘ，Ｙ方向的加速度，最小可测量加速度为２μｇ／Ｈｚ。在开环条件下器件的共振频率为９００Ｈｚ，频带宽度在０２００Ｈｚ之间。芯片的几何尺寸约为４×４ｍｍ。     

Low-power-Consumption metal oxide NO2 gas sensor based on micro-heater and screen printing technology

An NO2 micro gas sensor was fabricated based on a micro-heater using tin oxide nano-powders for effective gas detection and monitoring system with low power consumption and high sensitivity. The processes of the fabrication were acceptable to the conventional CMOS processes for mass-production. Semiconducting SnO2 nano-powders were synthesized via the co-precipitation method; and to increase the sensitivity of the NO2 gas rare metal dopants were added. In the structure of the micro-heater, the resistances of two semi-circular Pt heaters were connected to the spreader for thermal uniformity. The resistance of each heater becomes an electrically equal Wheatstone-bridge, which was divided in half by the heat spreading structure. Based on the aforementioned design, a low-power-consumption micro-heater was fabricated using the CMOS-compatible MEMS processes. A bridge-type micro-heater based on the Si substrate was fabricated via surface micro-machining. The NO2 sensing properties of a screen-printed tin oxide thick film device were measured The micro gas sensors showed substantial sensitivity down to 0.5 ppm NO2 at a low power consumption (34.2 mW).     

磁性复合材料的制备技术与研究进展

磁性复合材料是当前最活跃的新型材料,综述了当前磁性复合材料的研究现状,重点阐述了磁性复合材料的制备技术和特点,以及国内外最新的研究成果,并展望了其应用前景.     

A Fully Integrated Ring-Type Fluxgate Sensor Based on a Localized Core Saturation Method

This paper reports a new micromachined fluxgate sensor with extremely low power consumption, based on a localized core saturation method. The extremely low power consumption is achieved by quick saturation at the localized core region associated with sensing coils 10 times smaller than the excitation coils. We designed and optimized the sensor by using the electromagnetic simulation software MagNet, and we compared the simulation results with the experimental results. The device exhibits a power consumption of ~14 mW, a sensitivity of 650 V/T at 60 muT, and a sensor span of ~200 muT. In comparison with previously reported micro fluxgate sensors, the newly developed sensor consumes 7 times less power, but at the expense of sensor span and linearity     

Tunable Reverse‐Biased Graphene/Silicon Heterojunction Schottky Diode Sensor

A new chemical sensor based on reverse‐biased graphene/Si heterojunction diode has been developed that exhibits extremely high bias‐dependent molecular detection sensitivity and low operating power. The device takes advantage of graphene's atomically thin nature, which enables molecular adsorption on its surface to directly alter graphene/Si interface barrier height, thus affecting the junction current exponentially when operated in reverse bias and resulting in ultrahigh sensitivity. By operating the device in reverse bias, the work function of graphene, and hence the barrier height at the graphene/Si heterointerface, can be controlled by the bias magnitude, leading to a wide tunability of the molecular detection sensitivity. Such sensitivity control is also possible by carefully selecting the graphene/Si heterojunction Schottky barrier height. Compared to a conventional graphene amperometric sensor fabricated on the same chip, the proposed sensor demonstrated 13 times higher sensitivity for NO₂ and 3 times higher for NH₃ in ambient conditions, while consuming ～500 times less power for same magnitude of applied voltage bias. The sensing mechanism based on heterojunction Schottky barrier height change has been confirmed using capacitance‐voltage measurements.     

Magnetic Field Dependence of a Capacitance Temperature Sensor

The influence of a magnetic field on the capacitance of a glass-ceramic temperature sensor (Lake Shore CS-501GR) has been measured extensively at temperatures down to 0.09 K and magnetic fields up to 12 T. While the influence of a magnetic field is still negligible at 4 K, the sensor shows an increasing non-monotonic dependence on the magnetic field with falling temperature. The maximum relative change of capacitance with respect to the zero field value remains smaller than 5 · 10⁻⁴. However, with the given sensitivity of the sensor, this small magnetoeffect may not be ignored in the low temperature region.     

Design of a Low-Power Micromachined Fluxgate Sensor Using Localized Core Saturation Method

Design of a low-power micromachined ring-type flux- gate sensor with localized saturation cores has been made and optimized in this work. The design is accomplished by using the electromagnetic simulation software, Magnet^TM, which is capable of establishing a quantitative connection between the sensor parameters and the geometrical parameters of the model. Using recently developed data extraction techniques, the design with low power (19 mW) and high sensitivity (590 V/T at 60 muT) can be achieved after a series of simulations. For comparison, an actual device has been fabricated with sensitivity of 650 V/T at 60 muT, power consumption of 14 mW. The good agreement between the simulation and the experimental results validate our new approach for the design of low-power fluxgate. In addition, measurements using a second-harmonics-based detection circuit have been performed so that the noise, stability, and perming effect of the fabricated device are explored.     

基于峰值检测的MEMS器件微弱电容检测电路

针对MEMS器件研制中微弱信号的检测问题,提出了一种适用于电容式MEMS器件的微弱电容检测电路.此电路采用峰值检测技术,原理及结构简单;只检测待测电容的变化量,既可用于差分式检测,也可应用于单一待测电容的情况.首先利用正弦载波信号和微分电路对电容量进行载波调制,再通过减法电路得到幅值与电容变化量成比例的正弦信号,最后采用峰值检测方法解调信号,得到直流量输出.利用微小可调电容进行标定,结果表明检测电路的线性度良好,灵敏度约为3.631V/pF,精度达到0.2%.利用该检测电路检测MEMS陀螺上振动频率为2.85kHz的梳齿驱动器的电容量变化,输出信号频率为（2.85±0.02）kHz,误差低于0.7%,说明该电路能够应用于MEMS器件的微弱电容检测.     

扭摆型谐振式磁强计及其激振与测控系统设计

研究了基于扭摆式结构的谐振式磁强计及其激振与测控系统,设计了扭摆式谐振磁强计的基本结构,其对称式结构能够抑制加速度对磁场检测的干扰．设计了L形梁来释放加工过程中的应力,推导了开环系统和闭环系统的传递函数,通过初步参数设计,对扭矩随线圈匝数的变化进行了仿真,并介绍了基于对被测信号进行调制和同步解调的电容检测原理．结果表明,该谐振式MEMS磁强计灵敏度和分辨率高,多匝线圈方案使器件灵敏度大幅度提高,10匝线圈时的扭矩是单匝线圈的8倍,磁强计分辨率优于30nT．     

A Fluxgate Magnetic Sensor: From PCB to Micro-Integrated Technology

In this paper, a double-axis micro Fluxgate magnetic sensor is presented. The device represents an evolution of a PCB dual axis sensor previously realized. In the PCB version the experimental results exhibit excellent agreement with the simulations performed using a tool based on the finite element method. Using the same design approach a version of double-axis Fluxgate structure is here proposed to be realized in IC technology. The accurate study of the magnetic field distribution allows a 75% area saving for the IC version with respect to a direct scaling of the PCB version. Imposing an external magnetic field of about 60 muT, the simulated differential output voltage of the micro-integrated Fluxgate sensor achieves a peak value of 1 mV with 5 mA sinusoidal excitation current peak at 100 kHz. The integrated microstructure shows a linearity error of about 1.15% of the full scale, in the range of plusmn50 muT, with a sensitivity of about 0.45 mV/muT     

Optical fiber magnetic field sensor based on multi-mode fiber and core-offset structure

A magnetic field sensor based on a magnetic fluid (MF)-coated intermodal interferometer is proposed and experimentally demonstrated. It is fabricated by a core-offset structure between two segments of multi-mode fibres (MMF), a spherical structure is formed in the end of the second segment MMF. The core-offset section can be used to excite the core mode to the cladding, then the core and cladding modes will interference at the spherical structure due to the optical path difference caused by the refractive index difference. Two interference valleys of the interferometer integrated with MF under different magnetic field intensities have been experimentally analysed. The experimental results exhibit that the sensor possesses a magnetic field sensitivity of ?0.187 nm/mT by monitoring the wavelength shift at the magnetic field intensity from 0 to 20mT, and the optical power attenuation at specific wavelength with a magnetic field has a maximum sensitivity of 0.228 dB/mT.