A new silicon gas-flow sensor based on lift force

This paper presents the first silicon-flow sensor based on lift force. The sensor is a bulk-micromachined airfoil structure that uses the lift force as a sensing principle. The lift force acts normal to the flow in contrast to drag-force sensor types, where the force acts in the flow direction. The sensor utilizes the special distribution of the lift force along the length of the sensor structure. Since the sensor, like an airfoil, is mounted at a small angle to the flow, it induces very little flow disturbance. The sensor consists of two plates connected to a center beam. Each plate is 5×5-mm square with a thickness of 30 μm. The flow-induced forces deflect the two plates in the same direction, but with different magnitude. The deflections are detected by polysilicon strain gauges. The differential mode bridge makes the sensor insensitive to common mode deflection, e.g., acceleration forces. The lift-force principle is characterized using fundamental airfoil theory. The sensor has been experimentally verified, and a flow sensitivity of 7.4 μV/V/(m/s)² has been measured in both flow directions     

Vibration modes of a resonant silicon tube density sensor

We present an investigation of the resonance parameters for a new sensor for on-line measurements of fluid density. The sensor consists of a tube system made of single crystalline silicon. The tube system is excited electrostatically into mechanical resonance and the vibration is detected optically. Using a simplified theoretical analysis, the resonance frequency can be shown to be proportional to 1√ρ, where ρ is the density of the silicon and the fluid weighted according to their areas in a cross section of the tube. Thus, a change in fluid density results in a change in the resonance frequency. This dependence is demonstrated by measurements for four different vibrations modes. The quality of the vibration is also investigated through measurements of the Q-values of the vibration modes. The tubes are made using anisotropic silicon KOH etching and silicon-to-silicon fusion bonding micromachining techniques. The dimensions of the tube system are 8.6×17.7 mm with an outer tube thickness of 1 mm and a wall thickness of 100 μm. Total tube length is 61 mm, and the sample volume is 0.035 ml. The sensor has a very good density sensitivity of the order of -200 ppm/(kgm^-3) and a high Q of the order of 3000 for air in the tube     

A MUMPs angular-position and angular-speed sensor with off-chip wireless transmission

 A novel surface-micromachined non-contact high-angular-speed sensor with total surface area under 4 mm² was developed using the multi-user MEMS processes (MUMPs), and was integrated with a commercial RF transmitter with carrier frequency of 433 MHz for wireless signal detection. This piezoresistive sensing system is capable of wirelessly measuring rotation speeds with sensitivity of ∼2 Hz/rpm/V using 5 V input in the 100–6000 rpm rotation range. Further experimental analyses showed that a sensor designed with a 13 μg seismic mass has high enough sensitivity to detect angular position of a rotating disk if the disk rotation axis is tilted away from the vertical direction. Experimental results from simultaneous detection of angular position and average angular speed for the sensor are reported in this paper. Received: 5 May 2000/Accepted: 31 August 2000     

A new edge-detected lift force flow sensor

A lift force gas flow sensor which uses the force normal to the fluid flow to measure the flow velocity has recently been introduced. Two thin plates mounted at an angle are deflected when they are subjected to fluid flow. For most mechanical flow sensors the flow sensitivity is closely connected to the time response. A weaker structure gives higher flow sensitivity but a lower natural frequency, i.e., a slower response time. The lift force sensor is designed for measurements of respiratory gas flow in ventilators, where, in addition to low flow restriction, both high sensitivity and fast response are required. A new type of suspension has now been realized for the lift force flow sensor. The detection is separated from the suspension of the airfoil plate with the strain gauges placed on separate detector beams. This leads to separate parameters for optimization of the lift force concept with "independent" control of flow sensitivity and natural frequency. This paper presents an analytical model, simulations and measurements on the new structure. The new edge-detected sensor has been experimentally evaluated for different lengths (100-600 /spl mu/m), widths (20-100 /spl mu/m) and thicknesses (8-20 /spl mu/m) of the detector beams. In accordance with the theory, the measurements show that the new structure has approximately three times the natural frequency of the old, center detected structure and similar or improved flow sensitivity. The evaluation has also resulted in a design scheme for optimal performance. A flow sensitivity of 0.65 /spl mu/V/V/(l/min)/sup 2/ has been obtained for the best edge-detected sensor with a natural frequency of 3.2 kHz.     

硅微电容式二维加速度传感器的加工与测试

设计了一种基于体硅加工技术的单敏感质量元差分电容式二维加速度传感器,并采用硅-玻璃静电键合、ICP工艺释放等技术完成了二维加速度传感器的加工。测试结果表明:该二维加速度传感器两个检测方向上的灵敏度基本一致,线性度较好,交叉干扰较小。X、Y方向的灵敏度分别为58.3 mV/gn、55.6 mV/gn;线性相关系数分别为0.9968、0.9961,交叉灵敏度分别为6.17%、7.82%。     

A high-sensitivity z-axis capacitive silicon microaccelerometerwith a torsional suspension

This paper presents a new z-axis high-sensitivity silicon-micromachined capacitive accelerometer fabricated using a three-mask dissolved-wafer process (DWP). It employs capacitive sensing using overlap-area variations between comb electrodes and a torsional suspension system to provide high sensitivity without compromising bandwidth, full-scale range, or the pull-in voltage ceiling. Excellent electrical sensitivity is obtained by using high-aspect-ratio comb fingers with narrow air gaps of 2 μm and a large overlap area of 12 μm ×300 μm. Torsional suspension beams 150 μm long with a cross-sectional area of 12 μm ×3 μm are used to improve the mechanical gain. Simulations of the capacitance between sense fingers show a highly linear region over a wide 14-μm tip deflection range. Accelerometers were fabricated and yielded sensitivities of 263-300 mV/g, a nonlinearity less than 0.2% over a range of -4 to +3 g, a full-scale range of -4 to +6 g, and pull-in voltages greater than 8 V. A 3 dB cutoff frequency of 35 Hz was measured in air. The calculated thermomechanical noise in the sensor is 0.28 mg over this bandwidth     

阵列式MEMS仿生矢量振动传感器研究

针对在同一个物理测试过程中,往往会遇到很多所需测量振动信号的大小和频率在大范围内变化,而一个振动传感器很难满足测试要求的情况,提出了一种四单元集成阵列式仿生矢量振动传感器,4个微结构传感器量程分别为:10,100,500,1 000 gn。在分析敏感结构数学模型的基础上,用ANSYS软件对阵列敏感元件进行仿真,最后对加工好的传感器进行了相关的测试。测试结果表明:该阵列式振动传感器在二维方向的灵敏度高,线性度好,输出稳定性好。量程为100 gn传感器x向灵敏度为2.6134 mV/gn,线性度为0.99991,y向灵敏度为2.5563 mV/gn,线性度为0.99968。     

流场中沿轴向运动圆柱的附加质量计算

分别计算理想流体和黏性流体中沿轴向运动圆柱的附加质量.基于相对运动原理得出在无限流体域中不同长细比圆柱的附加质量,验证附加质量与流体黏性无关的这一结论,并发现长细比越大,附加质量因数越小.利用动网格技术的数值模拟结果表明:圆管中沿轴向运动圆柱的附加质量随管径比减小而增大,且流体的流动形态会对物体的附加质量产生一定的影响.以长细比和管径比为参数给出无限和有限流体域中圆柱附加质量与相应参变量的拟合函数.     

三梁-质量块敏感结构高性能压阻式碰撞加速度计

研究了一种主要应用于碰撞测试领域的硅微机械高性能压阻式加速度计,量程范围为2 000 gn.为满足技术性能要求,加速度计采用一种三梁-质量块结合梳齿阻尼器的新颖结构,从而可以同时具有高灵敏度及高动态特性(包括高谐振频率及精确阻尼控制).这种加速度计采用n型(100)普通硅片制作,主要工艺过程包括双面ICP深刻蚀和压阻集成工艺.振动台测试结果表明,加速度计的灵敏度为0.11 mV/gn/5 V,谐振频率为31 kHz,灵敏度±5%变化下平坦带宽大于5 kHz.采用落杆测试法测试了加速度计的冲击响应及0～2 000 gn满量程范围内的非线性度.封装后的加速度计承受15 000 gn的冲击测试后没有受到损坏.     

Cross-axis sensitivity reduction of a silicon MEMS piezoresistive accelerometer

This paper presents realization of a MEMS piezoresistive single axis accelerometer using dual doped TMAH solution. The silicon micromachined structure consists of a heavy proofmass supported by four thin flexures and sandwiched between top and bottom glass plates. Boron diffused piezoresistors located near fixed points of the flexure are used for sensing the developed stress due to applied acceleration. Based on the initial results an improved design has also been considered to achieve reduced cross-axis sensitivity and nonlinearity. The fabricated sensor tested upto 13 g acceleration shows average sensitivity of 0.556 mV/g along normal to the proofmass plane. The measured cross-axis sensitivity was 3.272 μV/g for X-axis and 3.442 μV/g for Y-axis which is less than 1% of Z-axis sensitivity. Comparing two designs there was an improvement of 63% sensitivity along Y-axis for the design with flexures placed along the proofmass edges.     

基于SOI技术梁膜结合高过载压阻式加速度计研究

采用微型机械电子系统技术和集成电路工艺制作出了SOI技术高灵敏度的硅微固态压阻平膜芯片;通过动力学分析和有限元模拟,研制出了具有高过载保护功能的加速度传感器结构;通过玻璃粉烧结工艺将其键合在弹性梁的应力集中处,研制出量程为±2000 g、过载能力为30倍满量程的高过载梁膜结合压阻式加速度计.加速度计具有较高的测量灵敏度和精度,满量程输出为126.97 mV/2V,静态精度为0.86%FS.     

A novel out-of-plane MEMS tunneling accelerometer

A novel out-of-plane MEMS tunneling accelerometer is designed, fabricated and characterized. ICP process, which can generate large proof mass, is used for the first time to fabricate an out-of-plane tunneling accelerometer. To reduce the high Hooke's constant in out-of-plane direction of the ICP etching structure, the beams and the proof mass are dry-etched by double mask ICP process, which reduce the Hooke's constant, thereby enhance the sensitivity of the device. The tunneling current of open loop is tested in the air by HP4145B semiconductor analyzer, which verifies the presence of tunneling current and shows the needed driving voltage. The close-loop test shows sensitivity of 811 mV/g for feedback voltage (the sensitivity of actuate voltage is about 200 mV/g) and nonlinearity of 1% in the measurement range of 0 to +1 g. The spectrum measurement is performed in general environment and the resolution of the device is 0.5 mg/rtHz (1.25–100 Hz), which shows better low frequency property.     

Dynamic and kinematic viscosity measurements with a resonating microtube

This paper examines the use of a micromachined resonating tube to measure both the dynamic viscosity and density of a fluid enabling the calculation of the kinematic viscosity. Dynamic viscosity is measured using the damping effect that a fluid has on the motion of the resonating tube. Fluid damping requires a change in drive voltage to maintain a constant vibrational amplitude. The density is measured via the change in resonant frequency caused by a change in fluid density while the viscosity is measured by monitoring the peak signal of the resonator. The dynamic viscosity measurement error between the new sensor and the calibration references ranges from 0.006 to 0.15 cP, or 0.6 to 8%. A variety of applications for the sensor will be discussed.     

基于地磁场探测的车辆监测系统

介绍了各向异性磁阻(AMR)传感器探测系统的检测电路的实现与数据信息处理方法。这种利用车辆通过道路时对地球磁场的影响来完成车辆检测的数据采集系统具有常规线圈检测器所不具备的优点,在智能交通系统(ITS)的信息采集中必将起着非常重要的作用。给出真实公路环境中对行驶中车辆探测的实验结果,实测效果直观明显,探测灵敏度达到2mV/V/Oe,线性度误差达到0.05%FS。     

Comparison analysis of energy loss between micro clamped–clamped and clamped-free beam in vertical motion flux modulation magnetic sensor

The 1/f noise is one of the main noise sources of giant magnetoresistive sensors, which will cause intrinsic detection limit at low frequency. To suppress this noise, a vertical motion flux modulation (VMFM) integrated with simple microelectromechanical-systems (MEMS) structure is proposed. However, the energy loss of VMFM structure is not considered yet. In this paper, energy loss between MEMS clamped–clamped beam (C–C beam) and clamped-free beam (C-F beam) used as VMFM structure are compared. In this comparison, quality factor (Q) is proposed to characterize the energy loss of the VMFM structure. Theory analysis and experimental results show that quality factor of a C–C beam is higher than that of a C-F beam, indicating a lower energy in VMFM. Finally, the sensitivity of a VMFM magnetic sensor modulated by a C–C beam is tested, and the sensitivity gets 3.85 mV/V/Gs.

     

闭环电流检测模块中Z轴TMR传感器的研制

阐述了灵敏方向垂直于芯片表面的Z轴TMR传感器的设计方法,并通过溅射镀膜及刻蚀工艺,在芯片表面电镀厚度、宽度、间距分别为为10 μm、10 μm、15 μm的NiFe聚磁层,研制出了Z轴灵敏的TMR传感器.通过实际测试,该方法制备的传感器在电源电压为5 V时,灵敏度达到了5 mV/Oe,证明了该设计方法的正确性.利用所研制的Z轴TMR传感器,构建了闭环电流检测模块,电流测量范围为0~100 A,测量误差小于0.3%.     

Piezoelectric cantilever microphone and microspeaker

A micromachined piezoelectric cantilever transducer, which works both as a microphone and as a microspeaker, has been fabricated and tested. The 2000×2000×4.5 μm³ cantilever has a zinc oxide (ZnO) piezoelectric thin film on a supporting layer of low-pressure chemical-vapor-deposited (LPCVD) low-stress silicon nitride. A highlight of the fabrication process, which may also be relevant for other micromachined structures, is the technique for producing a flat, multilayer cantilever. The measured microphone sensitivity is fairly constant at 3 mV/μbar in the low frequency range and rises to 20 mV/μbar at the lowest resonant frequency of 890 Hz. The 3 mV/μbar sensitivity is the highest reported to date for a microphone with a micromachined diaphragm. When measured into a 2 cm³ coupler with 4 V(zero-peak) drive, the microspeaker output sound pressure level (SPL) is 75 dB at 890 Hz. It increases to approximately 100 dB SPL at 4.8 kHz with 6 V(zero-peak) drive. The measured microphone frequency response agrees well with the results of an ABAQUS simulation     

Theoretical and experimental research on the in-plane comb-shaped capacitor for MEMS coriolis mass flow sensor

The Micro-Electro-Mechanical System Coriolis mass flow sensor uses a kind of in-plane comb-shaped capacitor to detect the vibration of tube containing the micro flow information. This paper takes the deflection of the micro tube caused by Coriolis force into account and models the in-plane comb-shaped capacitor of the sensor based on the electrostatic field method. Then the modulation and demodulation of the output capacitive signals are described in detail. The theoretical waveforms obtained by substituting the actual parameters into the models are consistent with the accepted conformal mapping method and match with the sampling signals, which attest the two models. According to the actual flow calibration experiment and the preliminary phase shift calculation, the measurement accuracy of the micro flow sensor reaches ±1.5 % with the repeatability of 0.75 % within 0–1.2 g/h flow range.     

Exploitation of aeroelastic effects for drift reduction,in an all-polymer air flow sensor

This paper presents a vibration amplitude measurement method that greatly reduces the effects of baseline resistance drift in an all-polymer piezoresistive flow sensor or microtuft. The sensor fabrication is based on flexible printed circuit board (flex-PCB) technology to enable the potential for low-cost and scalable manufacture. Drift reduction is accomplished by discriminating the flow-induced vibration (‘flutter’) amplitude of the microtuft-based sensor as a function of flow velocity. Flutter peak-to-peak amplitude is measured using a microcontroller-based custom readout circuit. The fabricated sensor with the readout circuitry demonstrated a drift error of 2.8 mV/h, which corresponds to a flow-referenced drift error of 0.2 m/s of wind velocity per hour. The sensor has a sensitivity of 14.5 mV/(m/s) with less than 1% non-linearity over the velocity range of 5–16 m/s. The proposed vibration amplitude measurement method is also applied to a sensor array with a modified structure and a reduced dimension, which demonstrated a sensitivity of 13.2 mV/(m/s) with a flow-referenced drift error of 0.03 m/s of wind velocity per hour.     

基于正弦力激励的预紧压电式力传感器的研究

为了校准预紧的压电式力传感器动态灵敏度并研究其频响特性和预紧结构的设计,首先介绍了正弦力激励的方法并建立校准数学模型。分别在传感器正立和倒立安装方式下进行测试,通过对比试验研究传感器端部等效质量引入的惯性力对传感器动态灵敏度的影响。然后根据传感器固有频率的落球测试方法,将传感器和附加质量块安装于振动系统。通过白噪声激励得到系统安装谐振频率,进而研究传感器有效频率范围和测量精度与安装谐振频率的关系。最后通过理论分析,说明传感器非对称设计的原因。试验结果表明,当附加质量块质量约为传感器质量的121倍时,可忽略端部等效质量对灵敏度标定的影响;压电式力传感器固有频率高达46kHz,但其有效使用频率范围受安装谐振频率限制,当试验频率与安装谐振频率比 时,压电式传感器精度等级为1%;传感器两端等效质量不同,预紧结构是非对称的,用于动态测试时要将端部等效质量轻的一端连接到被测物体。本研究结果可为开展传感器的现场标定和预紧结构的设计提供理论依据。