X-ray absolute calibration of the time response of a silicon photodiode

The time-dependent response of a 1-mm2 silicon photodiode was characterized by use of pulsed synchrotron radiation in the 4- to 16-nm-wavelength range. Modeling the input radiation pulse and the electrical response of the photodiode allowed the photodiode's capacitance as a function of wavelength and applied bias voltage to be determined. The capacitance was in the 7- to 19-pF range and resulted in response fall times as small as 0.4 ns. The capacitance determined by pulsed x-ray illumination was in good agreement with the capacitance determined by pulsed optical laser illumination. The absolute responsivity was measured by comparison with the responsivity of a calibrated photodiode.     

传感器固有频率和阻尼对冲击加速度检测的影响

研究了硅微机械高g(g为重力加速度)加速度传感器的固有频率和阻尼特性对冲击响应的影响。传感器固有频率低,阻尼小时,冲击加速度的响应波形包含传感器共振波,造成测量干扰。采用有适当阻尼,固有频率高的双质量块结构高g加速度传感器,进行接近2万g加速度峰值的一系列落杆冲击实验,都未见共振响应。同样的传感器制作成欠阻尼,进行实验时,发现共振干扰。该实验所用的传感器芯片面积小,固有频率高,调整该结构的弹性梁厚度,可制作量程为2×103g～2×105g的加速度传感器。     

新型谐振式硅微机械加速度计

制作出一种新型结构的谐振式硅微加速度计，其输出频率信号可以克服微机电系统器件输出微弱信号检测的困难、采用双端固定音叉作为谐振器，在加速度作用下，质量块的惯性力通过悬臂梁施加于音叉轴向，利用音叉谐振频率的变化测量加速度．在每个音叉臂上制作了梳齿结构，用梳齿间的静电力激励音叉产生谐振，并利用其构成的电容检测其振动频率．该加速度计采用体硅工艺制作，文中给出了工艺流程、用有限元方法仿真估算，得到传感器的灵敏度约为2／gHz．     

Design optimization and implementation of a microgravity capacitive HARPSS accelerometer

This paper reports on the design optimization and implementation of a lateral capacitive accelerometer with high sensitivity and micro-g resolution, fabricated through the high-aspect ratio polysilicon and single-crystal silicon process on regular silicon wafers. A new implementation of vertical corrugation in silicon electrodes is developed to reduce the mechanical noise equivalent acceleration of the sensor. The predicted effect of corrugation on thermomechanical noise and also on static sensitivity is verified using ANSYS steady-state thermal simulation and FEMLAB linear stationary electrostatics analysis, respectively. The number of corrugated electrodes and the sense gap spacing is optimized to minimize the system (sensor + circuit) noise floor, while satisfying process and electronics limits. The open-loop differential sensitivity of a 60-/spl mu/m-thick prototype accelerometer is measured to be 0.25 V/g equivalent to 4.5 pF/g over a 1-g range. The estimated total noise equivalent acceleration of the system (sensor + circuit) is 0.95 /spl mu/g//spl radic/Hz in atmosphere.     

Evaluation of a Capacitance Scaling System

An improved error analysis of an existing capacitance scaling system for supporting measurements of higher valued (10 nF to 100 ) ceramic-dielectric four-terminal-pair (4TP) capacitance standards over the 100-Hz to 100-kHz frequency range is described. The capacitance scaling system uses a commercial impedance (inductance-capacitance-resistance) meter and a single-decade inductive voltage divider as an impedance comparator. Four-terminal-pair capacitors in decade (10 : 1) steps from 10 nF to 100 F are measured. The system's 10 : 1 scaling error is determined using 100-pF and 1-nF air-dielectric 4TP capacitance standards with known capacitance and loss characteristics over frequency. This paper discusses the significant reductions in measurement uncertainty that were attained through the use of improved calibration standards and measurement method refinements. Details of the uncertainty analysis for a 10-nF capacitor (in the 100-Hz to 10-kHz frequency range) and verification data are presented.     

A switched-capacitor interface for capacitive pressure sensors

A switched-capacitor interface for a capacitive pressure sensor is developed which provides a linear digital output. It consists basically of a sample/hold circuit followed by a charge-balancing analog-to-digital converter. The sensor capacitance changes hyperbolically with an applied pressure. To convert the nonlinear capacitance change into the linear digital output, two linearization methods are investigated. In either method, a linear digital output with an accuracy higher than 8-b is obtained. Because of its high-accuracy capability and compatible fabrication process, the interface described is best suited for a smart silicon capacitive pressure sensor     

Miniature Accelerometer and Multichannel Signal Processor for Fiberoptic Fabry–Pérot Sensing

A miniature accelerometer based on silicon microelectromechanical systems (MEMS) fabrication technology has been developed. Using a beam-suspended proof mass and a Fabry-Peacuterot sensing gap, this accelerometer is fiber coupled to a miniature, multichannel, optical readout system which was developed for application in compact optical sensor systems. The approximately 4 mmtimes7 mmtimes2 mm accelerometer can be tailored to cover milli-g to kilo-g acceleration ranges. The miniature readout system is enclosed in approximately a 2 cmtimes8 cmtimes1 cm package, one of the smallest ever reported, and implements the complete optical path for a three-channel embodiment of a multichannel, highly sensitive and accurate, in-phase and quadrature (IQ) optical measurement system for Fabry-Peacuterot sensors. A variety of fiber-based sensors (temperature, strain, pressure, etc.) are commercially available using this Fabry-Peacuterot technique. The complete measurement system with the accelerometer was tested using a shaker table. Sample results are presented for 100 Hz, 10-g peak-peak acceleration     

压阻式硅微二维加速度计的加工与测试

提出了一种压阻式的硅微二维加速度计,该加速度计采用4个相互垂直的悬臂梁支撑中间有刚硬柱体的结构,利用合理布置的压敏电阻构成的惠斯通电桥测量水平面内两个方向的加速度．结合微结构的力学分析模型以及压阻原理分析了加速度计的灵敏特性、采用硅微机械加工工艺完成了加速度计的加工,应用微系统分析仪、激光拉曼光谱应力测试仪以及振动台分别对加工出的微结构形貌、残余应力、频响以及灵敏特性进行了相关测试．测试结果表明,两个方向的输出值均灵敏度高、线形度较好,胸灵敏度为1、0174mV／g（g为重力加速度）,线性系数为0．99991,y向灵敏度为0．89761mV／g,线性系数为0．99945．微加速度计的频响曲线较为平坦,其共振频率大约为670Hz．     

带有力反馈控制的三明治式微机械干涉加速度计

设计了一种静电力反馈控制的三明治式微机械干涉加速度计,加速度计由敏感芯片、半导体激光器、光电二极管以及相应的驱动电路和反馈控制电路组成.敏感芯片为玻璃-硅-玻璃3层结构,通过硅-玻璃键合体硅工艺制成.硅质量块由铝梁支撑,底部玻璃基片上有金属光栅和电极,通过在质量块和底部玻璃基片上的电极之间施加电压可以调节质量块与玻璃基片间的间隙.入射激光照射到敏感芯片上的光栅上,产生衍射光束,其光强随质量块与下玻璃的间距而变化.反馈控制电路通过测量衍射光强的变化来改变质量块与底电极之间的电压,使得质量块与底部玻璃基片的距离保持为入射光波长1/8的奇数倍,从而提高输出线性度,改善灵敏度,增大量程.     

Optical fiber accelerometer based on a silicon micromachined cantilever

An intensity-modulated fiber-optic accelerometer based on backreflection effects has been manufactured and tested. It uses a multimode fiber placed at a spherical mirror center, and the beam intensity is modulated by a micromachined silicon cantilever. This device has applications as an accelerometer and vibrometer for rotating machines. It exhibits an amplitude linearity of ±1.2% in the range of 0.1-22 m s(-2), a frequency linearity of ±1% in the range of 0-100 Hz, and a temperature sensitivity of less than 0.03%/°C. The sensor is devoted to a wavelength-division multiplexing network.     

微型静电悬浮Z向加速度计的计算机模拟

本工作针对一种新型的电容式力平衡加速度计－微型静电悬浮Ｚ向加速度进行了计算机模拟。模拟中的Ｚ向加速度计拟采用微机械加工技术在硅片上制作，利用静电悬浮原理平衡质量块，感应加速度并输出信号。计算机模拟分析了加速度计的悬浮特性，稳定特性，响应特性。对Ｃ－Ｆ转换电路的输出特性也进行了分析，该电路可用ＣＭＯＳ工艺集成在加速度传感器的周围。模拟结果表明该加速度计的悬浮特性，稳定特性，响应特性。对Ｃ－Ｆ转换电路     

A Silicon Thermal Accelerometer Without Solid Proof Mass Using Porous Silicon Thermal Isolation

A Si thermal accelerometer without solid proof mass, based on porous silicon (PS) technology has been developed and characterized. The device is compatible with silicon technology and it consists of a polysilicon heater and two thermopiles, situated symmetrically on each side of a heater. A thick PS layer provides thermal isolation from the Si substrate. The operation principle is based on the movement induced thermal convection variations between the heater and the hot thermopile contacts, which are caused by the movement of the hot fluid medium on top of the heater with respect to the sensor die. A detailed simulation by the FEA package Ansys was carried out in order to find the optimum geometrical parameters and the theoretical device behavior. The porous silicon thermal accelerometer (PSTA) was tested in a specially designed vibration system for various frequencies and accelerations. Different packaging configurations were also evaluated for both air and oil surrounding environments. The dependence of the PSTA response on applied power was studied for each surrounding environment. In each case, the response was compared with a commercial reference accelerometer and the corresponding sensitivities were extracted.     

Seismic Velocity Sensor With an Internal Sky-Hook Damping Feedback Loop

This paper presents a new seismic velocity sensor with an internal feedback control loop. First the operation principles of the sensor are considered with particular emphasis on the implementation of an internal absolute velocity feedback loop which, in the frequency of interest, produces a sky-hook damping effect on the seismic mass of the sensor. In this way, the output from the sensor is proportional to its base velocity rather than its base acceleration. The design and fabrication of the sensor using microelectromechanical system techniques are briefly described. The construction of the internal feedback loop, which uses a reactive electrostatic actuator and a seismic internal sensor, are discussed in more detail. Finally the results of experimental tests are presented, which highlight that: a) in the frequency of interest, the output signal of the sensor is proportional to its base velocity; b) the fundamental resonance of the seismic sensor is attenuated by the active damping effect produced by the internal feedback control loop, and c) above this fundamental resonance, the response rolls off at a rate of 3 dB per decade and lags by 90$^{circ }$ instead of the 180$^{circ}$ phase lag of a standard seismic accelerometer sensor.      

低量程高线性压阻式微机械加速度传感器

介绍了一种低量程高线性压阻式微机械加速度传感器的设计、工艺制作和封装 ,还较详细地介绍了静态和动态特性的测量和结果。为提高灵敏度,传感器采用悬臂梁结构。本文对结构的固有横向效应进行了计算,结果表明此种结构的三种横向效应主要是由于质量块（岛）质心偏离梁中平面,沿梁伸展方向（ x向）惯性力分量产生的弯矩所致。提出了调整上下盖板与中间质量块之间的气隙改善器件频响特性的方法。报道的压阻式微机械加速度传感器量程± 1g(g为重力加速度 ), 线性度优于 0.05％,灵敏度约 1mV/gV,阻尼比 0.7,带宽 110Hz。     

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.     

一种新型高灵敏度横向电容式硅微加速度计

提出了一种新型高灵敏度横向电容式硅微加速度计．根据差分电容极板间正对面积的改变来检测加速度大小．保证输出电压与加速度之间的线性度．系统刚度可由静电力调节、为了提高电学灵敏度,在检测电容极板上设计高K介质层,增大了检测电容量,减小了杂散电容的影响．使用Coventor Ware对本设计进行机械分析、力电耦合分析和模态分析,仿真结果与理论计算相吻合．加速度计使用简单的表面牺牲层工艺即可完成,具有很好的发展前景．     

A Novel Threshold Accelerometer With Postbuckling Structures for Airbag Restraint Systems

Based on the postbuckling theory of large deflection beams, the nonlinear stiffness of a postbuckling beam is deduced and in agreement with the results of buckling experiments. Then, a novel post machined threshold accelerometer is designed, which consists of eight oblique post beams with an inertial mass in the middle to ensure its single moving direction and an electrical contact part fabricated on the bottom of the inertial mass. The threshold accelerometer is an integration of a threshold sensor and an inertial driven actuator used in airbag restraint systems. When the acceleration reaches the threshold, the beams buckle and close the threshold accelerometer, and when it gets down to be a certain value, the accelerometer opens quickly under the effect of the elastic force developed by the postbuckling beams. Compared with the design models of other threshold accelerometers with linear beam structures, the nonlinear postbuckling beams are introduced as threshold sensing elements. A number of design factors such as the air film damping and the contact force are taken into full consideration, thus establishing the dynamic equation of the accelerometer under coupled forces. The dynamical simulation for the strong nonlinear system with elliptic integrals indicates its good threshold characteristic and high contact reliability. The threshold accelerometer responds within 4 ms when it is triggered by a threshold acceleration ac = 20 g, and cuts off quickly when the cutoff acceleration is under ad = 5 g. Meanwhile, the unstable contact time is only 0.02 ms for the contact force to reach 50 mN, which guarantees the contact resistance to be less than 20 mOmega. With the results of the dynamic simulation, supported by previous buckling experiments, the accelerometer can provide accurate threshold sensing without false actuations under interferences outside, especially electromagnetic and vibration interferences, and hence their wide applications in safe-arming systems.     

A resonant accelerometer with two-stage microleverage mechanisms fabricated by SOI-MEMS technology

We present the design, fabrication, and testing of a push-pull differential resonant accelerometer with double-ended-tuning-fork (DETF) as the inertial force sensor. The accelerometer is fabricated with the silicon-on-insulator microelectromechanical systems (MEMS) technology that bridges surface micromachining and bulk micromachining by integrating the 50-/spl mu/m-thick high-aspect ratio MEMS structure with the standard circuit foundry process. Two DETF resonators serve as the force sensor measuring the acceleration through a frequency shift caused by the inertial force acting as axial loading. Two-stage microleverage mechanisms with an amplification factor of 80 are designed for force amplification to increase the overall sensitivity to 160 Hz/g, which is confirmed by the experimental value of 158 Hz/g. Trans-resistance amplifiers are designed and integrated on the same chip for output signal amplification and processing. The 50-/spl mu/m thickness of the high-aspect ratio MEMS structure has no effect on the amplification factor of the mechanism but contributes to a greater capacitance force; therefore, the resonator can be actuated by a much lower ac voltage comparing to the 2-/spl mu/m-thick DETF resonators. The testing results agree with the designed sensitivity for static acceleration.     

The Design of Extremely Low-Noise Camera-Tube Preamplifiers

The design of current amplifiers suitable for amplifying the signal of camera tubes (or other similar transducers) is presented. Excellent noise performance can be obtained especially at low frequencies. Only one adjustment is required for shaping the frequency response and a very large bandwidth can be obtained. Experimental results are given for an amplifier designed for a camera tube with 15-pF output capacitance. The measured equivalent input noise current of this amplifier is smaller than 1 nA in a 5-MHz frequency band. The bandwidth of the amplifier exceeds 10 MHz.     

Spectroscopy for the Analysis of Nanoporous Silicon Gas and Humidity Sensors

In this work, a Raman spectroscopic study of nanoporous silicon sensor samples demonstrated its use as a method of gauging the sensor potential via quantitative data it provides on the sensor nanostructure dimensions. This special property of the Raman spectroscopy technique also showed its potential to determine mechanical stability of the samples over 3 months. This work also shows that the Raman spectroscopy technique is sensitive to step changes in relative humidity in all the sensor samples via its measurement of the strain-free crystalline silicon (c-Si) Raman peak. Since the Raman technique is non-destructive and senses remotely on the fragile nanoporous sensor samples it will be the ideal replacement of the presently used electrical capacitance techniques as the primary determination of relative humidity.