环境温度对气流式角速度传感器灵敏度的影响

采用有限元方法,计算了不同温度下敏感元件内的温度场和流场。结果表明:在输入恒定角速度时,敏感元件内的温度场和流场随环境温度发生变化,温度增加,在两个检测热电阻丝处的气流速度之差减小,检测电桥输出电压减小,传感器灵敏度降低;温度下降,在两个检测热电阻丝处的气流速度之差增加,检测电桥输出电压增加,传感器灵敏度增加。当输入角速度为20°/s时,传感器的灵敏度随温度平均变化率为0.0336mV/(°)·s–1·℃–1。     

三丝结构水平姿态传感器敏感机理的研究

采用有限元法,利用ANSYS-FLOTRAN CFD软件,计算了在不同倾斜状态下三丝结构敏感元件内的温度场和流场.计算结果表明,加热热电阻丝在敏感元件内形成一定的温度场和流场,倾斜时温度场和流场不再对称分布;在水平状态时两检测热电阻丝处的气流速度相等,两检测热电阻丝的电阻相等,电桥电路输出为零;在倾斜状态下时,两检测热电阻丝处的气流速度之差随着倾斜角度而变化,引起两检测热电阻丝电阻之差也随之变化,电桥输出一个对应于倾斜角度的电压.有限元计算法为三丝结构气流式水平姿态传感器优化设计开辟了有效的研究途径.     

敏感工作气体对射流陀螺灵敏度的影响

研究了干燥空气、N2和He等3种常用敏感工作气体对射流陀螺灵敏度的影响。采用有限元法计算了输入角速度ωi=20(°)/s时敏感元件内的流场。计算结果和实验表明,改变敏感元件内敏感工作气体的种类,流场分布也随之变化。ωi=20(°)/s时,两热电阻丝r1、r2处的气流速度差ΔvN2>ΔvAIR>ΔvHe。灵敏度系数KN2>KAIR>KHe,其中KN2=1.05 KAIR,KHe=0.21%KAIR。N2对应的灵敏度最高,热电阻丝抗氧化,稳定性较好,但成本高;干燥空气的灵敏度次之,热电阻丝易氧化,稳定性差;He对应的灵敏度最小,热电阻丝不易氧化,稳定性最好。该文解释了敏感工作气体对射流陀螺灵敏度的影响机理,为提高射流陀螺的实用性,满足不同工程需要开辟了一个新的途径。     

两丝球形气流式倾角传感器敏感机理的研究

采用有限元法(FEM)计算了两丝球形敏感元件内的温度场和流场,解释和验证了该结构传感器的敏感机理。计算结果和实验表明,两丝球形敏感元件内的流场和温度场随倾角θ发生变化;倾斜时等温线不再左右对称,高温等温线重叠部分减少;θ=0°时,热敏电阻丝r1、r2的平均温度差ΔT=0;θ=10°时,ΔT=7.31K;θ=20°时,ΔT=13.64K。ΔT随着θ变化的平均灵敏度为0.707K/(°);倾斜时位置偏高的热敏电阻丝平均温度高,θ和ΔT基本呈线性关系;与实测值相比,理论值偏大,平均相对偏差为4.5%;热敏电阻丝r1、r2的温度差ΔT随着倾角θ变化,引起两热敏电阻丝阻值改变,检测电桥输出一个对应于倾角θ的不平衡电压ΔV。该文采用的方法为两丝球形敏感腔结构气流式倾角传感器的结构优化和性能改进开辟了有效的研究途径。     

新型结构CO2传感器的研究

介绍了一种新型管式结构固体电解质CO2传感器。该传感器是将溶胶–凝胶法制备的NASICON材料均匀涂敷在Al2O3陶瓷管上,烧结形成厚膜,加热丝穿过管内提供热量。在加热电流为180 mA,CO2浓度为(200~2000)?06时,管式元件灵敏度曲线的斜率达到60,比同电流下平面型元件的斜率高出14.2。35 d内,管式元件在1 000?06浓度下的漂移值为8.8 mV,与平面型元件的漂移值11.3 mV相比,显示了较好的稳定性。     

应用于EMC测量的集成光学电场传感器性能分析

依据集成光学电场传感器的工作原理,研制了可用于电磁兼容性测量的分段电极结构与锥形天线结构的电场传感器.测试结果表明:分段电极传感器频响范围为10 MHz～6 GHz,最小可测电场强度达到30 mV/m,在频率为200 MHz时,线性动态范围可达90 dB;锥形天线传感器频响范围为10 kHz～10 GHz,最小可测电场强度达到20 mV/m,在频率为1 GHz时,线性动态范围可达100 dB.     

自加热非晶锗热电阻MEMS流速传感器的制造与测试

为扩大流速传感器的测量范围并降低功耗,制造并测试了一种基于自加热非晶锗薄膜热电阻的MEMS流速传感器,它是由嵌入氮化硅薄膜的四个非晶锗热敏电阻和一对环境测温补偿电阻组成。四个非晶锗热电阻同时作为自加热热源和测温元件,相互连接以形成惠斯通电桥。给出了MEMS工艺流程,微加工制造了尺寸为8.9 mm×5.6 mm×0.4 mm的流速传感器芯片。搭建了低流速和高流速气流通道实验装置,对传感器的惠斯通电桥施加50μA的恒定电流(CCA),实现了0～50 m/s范围内的流速测量。结果表明,传感器在低流速(0～2 m/s)时的灵敏度约为81.6 mV/(m/s),在高流速(2～50 m/s)时的灵敏度约为51.9 mV/(m/s),最大功耗仅约为1.03 mW。     

基于金刚石NV色心磁传感器微波调制频率优化的高灵敏度磁传感方法

基于金刚石氮空位(NV)色心系综的磁传感器磁场检测的绝对灵敏度与光探测磁共振(ODMR)的解调曲线的最大斜率呈反比,而解调曲线的斜率主要取决于磁传感器的调制参数。重点研究了磁传感器的灵敏度与调制频率之间的关系。介绍了NV色心的能级结构,根据其磁检测原理,采用基于微波频率调制解调的ODMR技术来检测外部微弱磁场。介绍了计算磁灵敏度的理论模型。通过实验证明,当激光功率为50 mW、微波功率为7 dBm、调制频率为18 kHz时,解调曲线的斜率为1.146 1 mV/kHz,相比于未优化前(0.086 8 mV/kHz)提高了约12.2倍。散粒噪声限制的磁传感器的灵敏度约为4 nT/Hz~(1/2)(理论计算结果约为1 nT/Hz~(1/2))。     

对数放大器理想特性直线拟合算法分析

结合对数放大器的对数斜率及动态范围等关键参数的定义,讨论了最小二乘法、最小一乘法及最佳直线法三种线性拟合法则在对数放大器测量中的应用,分析和验证了不同算法对理想特性直线及测量的影响。最佳直线法的最大绝对值最小法则相比于其他拟合法,更适用于线性区间和线性度的拟合,计算精度高,并在实例分析中得到验证。     

偏振方位角对光学脉冲磁场传感器灵敏度的影响

理论分析了光学脉冲磁场传感器中偏振方位角对灵敏度和信噪比的影响, 提出了用偏振方位角的大小来提高脉冲磁场传感器灵敏度的方法。实验结果表明, 当偏振方位角分别为45°, 60°, 70°和80°时对应的灵敏度为1.8/T,1.9/T,2.9/T和4.6/T,因此增加偏振方位角可提高磁场传感器的灵敏度。实验结果和理论分析相吻合,验证了此方法的正确性。     

含贯通线及PCB板开孔腔体的电磁耦合研究

外界能量通过贯通线进入开孔屏蔽体,与PCB上MSL耦合而生成感应电流(Current),加剧了对敏感器件的耦合伤害。故建立含贯通线及PCB板开孔屏蔽腔模型,进行多角度耦合特性计算。在建模有效性验证后,利用有限元法探讨平面波激励下PCB不同模型、MSL上不同端接电阻、贯通线半径、贯通线与腔体壁相接及多贯通线等参数变化对Current的影响规律。结果表明:双介质模型的使用更接近实际PCB 结构对场的影响;两端接电阻取值相差不大条件下,可不考虑与MSL的阻抗匹配,取值也可不相等;Current 数值随贯通线半径的增加而增加;贯通线与腔体壁不同表面相接对应Current幅值要远高于非接触的情况,并会激出新的谐振点。多根贯通线及线间距改变时Current幅值都要高于单线的情况,尤以第一谐振之前更为明显,多线存在不会影响谐振点出现位置。     

Reliability of thick Al wire bonds in IGBT modules for tractionmotor drives

Reliability enhancement of thick Al wire bonds during thermal fatigue test has been investigated from a metallurgical viewpoint. Al wire bonds degrade with the increase of crack length during thermal fatigue tests with high ΔT_j due to the tensile stress generated by the thermal expansion coefficient mismatch between Al wires and Si. It is also found that cracks propagate along the small grain boundaries of Al wires at the bonding interface. It is predicted that the Al wire bonds may not degrade due to thermal fatigue if ΔT_j is controlled below 40 K, i.e., keeping it within the actual temperature fluctuation range in IGBT modules for traction motor drives. The reliability of Al wire bonds can be enhanced by increasing the grain size of the Al wire at the bonding interface. The high temperature bonding is considered to be a good candidate for enhancing the reliability of Al wire bonds     

On optimal ordering of signals in parallel wire bundles

Optimal ordering and sizing of wires in a constrained-width interconnect bundle are studied in this paper. It is shown that among all possible orderings of signal wires, a monotonic order of the signals according to their effective driver resistance yields the smallest weighted average delay. Minimizing weighted average delay is a good approximation for MinMax delay optimization. Three variants of monotonic ordering are proven to be optimal, depending on the Miller coupling factors (MCF) ratio between the signals at the sides of the bundle and that of the internal wires. The monotonic order property holds for a very broad range of VLSI circuit settings arising in common design practice. A simple, yet near-optimal, setting of wire widths within the bundle to yield the best average weighted delay is proposed. The theoretical results have been validated by numerical experiments on 65 nm process technology and industrial design data. In all cases the ordering optimization yielded improvement in the range of 10% in wire delay, translated to about 5% improvement in the clock cycle of a high-performance microprocessor implemented in that technology.     

MEMS机油压力传感器可靠性研究

研究了封装工艺对传感器可靠性的影响。分析和实验结果表明,机油压力传感器封装材料及各个工艺步骤都会影响传感器的性能和可靠性。贴片胶性能不能满足可靠性要求,会引起传感器信号漂移和高温不稳定性;引线键合强度不够,在工作中会断裂;硅油化学稳定和耐温性能不够好,会造成传感器高温输出信号不稳定,硅油中的空气和杂质会造成传感器零点输出偏大,使传感器的精度下降等。     

Investigation of the thermal properties of thin solid materials at different temperature levels using a set of microresistors

The measurement of thermal properties of solid materials at different temperatures above ambient is investigated using a set of microresistors. Samples consisted of suspended films with sets of long, parallel resistive wires deposited on their surfaces. One resistive wire was heated by an alternating current. Surface temperature changes in DC and AC regimes were then detected by measuring the change in electrical resistance of the other wires deposited on the surface. The length of wires was chosen so that they may be assumed isothermal and such that heat diffusion acts perpendicularly to their axes. By measuring the dependence of the surface alternating temperature oscillation on the modulation frequency f and on the separation between the heating wire and the probing wires, the thermal diffusivity of the sample was determined. Through adjustment of the alternating current amplitude in the source wire, the temperature at which the thermal diffusivity of the sample was evaluated was finely controlled. For the validation of the method, pure silicon samples were first studied. An experimental bench was set up and resistive source and probes were experimentally characterized. Results obtained from ambient temperature to 500 K for pure silicon are in accordance with reference data found in the scientific literature.     

A square-diaphragm piezoresistive pressure sensor with arectangular central boss for low-pressure ranges

Describes the theory and experimental data for a piezoresistive low-pressure sensor featuring a variety of advantages. The objective of this development was a sensor with high sensitivity, high overload range, and good linearity. In comparison to familiar sensor types, the sensor developed for the pressure range of 10 kPa exhibits an excellent sensitivity of 35 mV/V FSO (full scale output) and nonlinearity <±0.05%. The sensor's theoretical performance was confirmed by measurements on manufactured pressure sensors     

A SQUID-Based Nondestructive Evaluation System for Testing Wires of Arbitrary Length

The high field sensitivity of superconducting quantum interference devices (SQUIDs), especially at low frequencies, makes them ideally suited for applications in nondestructive evaluation. For testing of conducting wires, such as aluminum bond wire, we developed a special cryostat, which allows for pulling a wire of arbitrary length (which is kept at room temperature) through a niobium flux transformer connected to a niobium dc SQUID. The wire is excited by either passing an alternating current through it, or by exciting eddy-currents in the wire. The cryostat is made from a stainless steel inner vessel; the outer tube is from fiberglass. The gradiometric pickup loops are wound on a German-silver tube. As the wire under test is at room temperature, thermal noise produced by the wire is limiting the sensitivity of the system, rather than thermal noise produced by the stainless steel dewar.     

Microstructural evolution of ultrasonically bonded high purity Al wire during extended range thermal cycling

This paper concerns the reliability of ultrasonically bonded high purity thick aluminium wires at elevated temperature. To date, the evolution of the microstructure of wire bonds during thermomechanical exposure and its influence on reliability have not been fully characterised and understood, particularly as they pertain to thermal cycling regimes which exceed 125 °C. Shear testing, indentation hardness and fine-scale microstructural data are reported here which show that the rate of wear-out can be influenced not only by the thermal cycling range (ΔT), but more importantly by the maximum temperature and duration to which bonds are exposed. There is evidence that significant annealing occurs during thermal cycling regimes with high T_max values, which results in the removal of some of the damage accumulated and a reduction in the rate of crack propagation. The rate of bond degradation is also found to be faster for 99.99% (4 N) than 99.999% (5 N) pure Al wires. Analysis of the two wire compositions after thermal cycling suggests that this difference could be attributable to a difference in their creep resistance. In conclusion, our findings suggest that high purity Al wire bonds may be suitable for operation at temperatures which exceed 125 °C.     

大功率LED排式热管散热器的开发及性能研究

开发了一种应用于大功率LED散热的排式热管散热器。在大空间自然对流冷却环境中,分别在0°、30°、60°、90°放置条件下对其启动性能、均温特性、散热性能进行了试验研究。试验结果表明:散热器启动性能良好,启动时间约为67min;在输入功率为30～70W的范围内,热源表面中心点温度不超过75℃;各倾角下散热器均具有较低的总热阻及扩散热阻,0°放置时总热阻最小。基于试验所得结果,通过计算LED结温论证了排式热管散热器在各倾角条件下均可满足热输出70W以下大功率LED散热的需求。