抑制气敏元件零点漂移的实用电路

一种利用闭环控制电路抑制气敏元件零点漂移的设计思想、原理框图及实验结果。该电路适用于起始阻值漂移，而灵敏度基本不变的气敏元件，可大大提高此类元件的稳定性与准确性。     

基于铌酸锂晶体自身角度光偏置的光学电压传感器

提出了一种利用单轴电光晶体自身角度光偏置的新型光学电压传感器,其光学传感单元由夹在两个正交偏振器之间的一个单轴电光晶体组成.与以往利用四分之一波片产生光偏置不同,新型电压传感器利用单轴传感晶体的自然双折射和近轴光束,将传感晶体沿电光双折射主轴方向转动一个小的角度,产生π/2的角度光偏置.因此,可在不需要附加四分之一波片的条件下实现电压的线性传感.利用单块铌酸锂晶体作为传感元件,对0.2 ～ 35 V交流电压进行测量的非线性误差低于1.8%.此外,计算表明基于铌酸锂晶体的π/2角度光偏置的温度漂移率低于普通多级石英波片.新型传感器简化了光学电压传感器结构,降低了成本,并避免了以往传感器中附加四分之一波片对传感器性能的不利影响.     

基于三次样条插值的硅压阻式压力传感器的温度补偿

传感器的零点温度漂移、灵敏度温度漂移和非线性误差是影响传感器性能的主要因素,如何能使该类误差得到有效补偿对于提高其性能有重要意义。提出了基于三次样条曲线插值的温度补偿方法,改进了传统三次样条曲线插值的补偿方法,分别对传感器的零点、灵敏度以及非线性进行补偿,用这种方法对测压范围为1.0140×105 Pa～3.0140×105 Pa,温度范围为-20℃～+60℃的硅压阻式压力传感器的实验标定结果进行了温度补偿。通过比较传统三次样条插值补偿后的传感器输出信号,验证了使用改进后的三次样条曲线插值法的补偿效果更好。这种方法为高精度压力传感器的温度补偿提供了一种有价值的理论依据。     

高速磁浮列车间隙传感器温度漂移的补偿

为了解决检测线圈电阻受温度影响而导致漂移补偿问题,设计分析了高速磁浮列车间隙传感器电路模型,设计补偿线圈,利用差分方式补偿了温度漂移,同时还分析得出了测量间隙对传感器温度灵敏度影响很小的结论,在传感器空载条件下的建立温度漂移修正表,利用该修正表来补偿传感器的温度漂移,通过这些措施,大大提高了间隙位移传感器输出信号的温度稳定性.     

Design, fabrication, and testing of VDP MEMS pressure sensors

In this paper, a four-terminal piezoresistive sensor commonly known as a van der Pauw (VDP) structure is presented for its application to MEMS pressure sensing. In a recent study, our team has determined the relation between the biaxial stress state and the piezoresistive response of a VDP structure by combining the VDP resistance equations with the equations governing silicon piezoresistivity and has proposed a new piezoresistive pressure sensor. It was observed that the sensitivity of the VDP sensor is over three times higher than the conventional filament type Wheatstone bridge resistor. To check our theoretical findings, we fabricated several (100) silicon diaphragms with both the VDP sensors and filament resistor sensors on the same wafer so both the sensor elements have same doping concentration. Several diaphragms had VDP sensors of different sizes and orientations to find out their geometric effects on pressure sensitivity. The diaphragms were subjected to known pressures, and the pressure sensitivities of both types of sensors were measured using an in-house built calibration setup. It was found that the VDP devices had a linear response to pressure as expected, and were more sensitive than the resistor sensors. Also, the VDP sensors provided a number of additional advantages, such as its size independent sensitivity and simple fabrication steps due to its simple geometry.     

0.2 mT Residual offset of CMOS integrated vertical Hall sensors

A residual offset lower than 0.2 mT is obtained with a CMOS integrated vertical Hall (VH)-sensor microsystem. Instead of the conventional design with five contacts in the sensor active area, we apply a layout with only four contacts. This design shows a higher effectiveness for the offset reduction by the spinning current (SC) method, because of the symmetrical current flow for the two different biasing phases. Furthermore, to obtain very low offsets, coupled sensors are integrated with the spinning current electronics in the final microsystem. A sensitivity up to S_v=0.025 V/VT is achieved for these sensors without any additional technology step. The measured output noise level of the integrated microsystem (1.9 μT/ ) is in the usual range of commercial integrated Hall-sensors. Our new developments open the way to the realization of compact, low-cost angular sensors with 10 bit resolution.     

低噪声放大器直流偏置电路的仿真设计实验

嗓声放大器(Low Noise Amplifier,LNA)是微波系统及其测量仪器中的关键部件之一,其噪声的大小直接影响信号接收灵敏度及系统的可靠性.在晶体管放大电路中,偏置电路为晶体管提供合适的静态工作点,偏置电路设计的重要性不可低估.主要介绍了低噪声放大器中直流偏置电路的仿真设计.     

Alternating biasing of SDT sensors

The spin dependent tunneling (SDT) effect has been observed in thin ferromagnetic multilayer structures. In general, two ferromagnetic layers are separated by a very thin non-conductive layer. In dependence on the angle between the magnetization of the upper and the lower ferromagnetic layer, electrons tunnel through the non-conductive barrier layer. We made experiments with an SDT sensor fabricated by NVE Corporation. Four elements in the bridge configuration are used in the sensor structure. One ferromagnetic layer of each element is pinned by an anti-ferromagnetic layer. The so-called orthogonal biasing can be applied in this sensor type. We also tried to study the possibilities of ac biasing techniques in the SDT sensors of this type.     

Recursive parameter estimation of exhaust gas oxygen sensors with input-dependent time delay and linear parameters

Exhaust gas oxygen sensors are widely used for emission control in internal combustion engine systems. Due to their working principle and their positioning, these sensors are subject to input-dependent time delays and input-dependent linear parameters. Consequently, the corresponding time delays and linear parameters can vary fast, i.e. at the same rate as the respective input signals. This paper presents an extension of an existing gradient-based least-squares algorithm and its application to recursively estimate the input-dependent time delays and linear parameters of wide-range oxygen sensors in diesel engines. The extended algorithm is applied in a detailed simulation and experimental study involving real wide-range oxygen sensors that are affected by drift, aging, clogging and manipulation. The input-dependent time delay and linear parameter estimates obtained with the proposed recursive algorithm accurately reproduce the estimates obtained with a numerical offline optimization procedure.     

Functional testing and characterisation of (bio-)chemical sensors on wafer level

An automated computer-assisted system for the functional testing and characterisation of (bio-)chemical sensors on wafer level is developed and integrated into a commercial prober station. The system enables the identification and selection of “good” sensors on wafer level and thus, allows to avoid further expensive bonding, encapsulation and packaging processes for defective or non-functioning sensor structures. Moreover, a specifically designed flow-through electrochemical microcell offers the possibility of wafer-level characterisation of (bio-)chemical sensors in terms of sensitivity, drift, hysteresis and response time at an early process stage. The system has been exemplarily tested using wafers combining pH-sensitive capacitive electrolyte-insulator-semiconductor structures as well as ion-sensitive field-effect transistors with different geometrical sizes and gate layouts.     

多孔Al2O3电容式湿度传感器 长期漂移的机理研究

本文通过对多孔Al_2O_3薄膜的显微结构形貌和晶相组成的跟踪检测,观察了多孔Al_2O_3薄膜几何结构和晶相的经时变化.对其原因进行了探讨,从而对多孔Al_2O_3电容式湿度传感器响应的长期漂移机理进行了详细讨论,并指出了克服或改善这类湿度传感器漂移的方向.     

厚膜压力传感器的结构优化

为提高厚膜压力传感器的稳定性,借助有限元分析软件Ansys,研究了厚膜压力传感器弹性体的应力分布,进而设计了应变电阻的尺寸,并优化了其布局。采用Ф18mm的96%A l2O3弹性体瓷件研制了一种新型厚膜力敏芯片,实验结果表明:它的热零点温漂小于3×10-4FS/℃,过载达120%,非线性误差及迟滞误差都小于±0.2%FS,精度由±0.4%FS提高到±0.2%FS,其线性度和稳定性得到很大提高,可广泛应用于仪器仪表、测控和导航等领域。     

磁致伸缩位移传感器双磁环间测量盲区的影响分析

为减小双磁环磁致伸缩位移传感器磁环间的测量盲区,对传感器在测量盲区内的输出信号进行了分析。从双磁环偏置磁场与磁环间距的关系进行研究,建立了双磁环磁致伸缩位移传感器的输出电压模型,计算了不同偏置磁场强度的双磁环在不同间距与放置方向时传感器的输出电压,并通过实验进行了验证。结果表明,磁环规格相同时,测量盲区的大小与磁环放置方向无关,磁环偏置磁场强度越小,磁环间的测量盲区越小,磁场叠加影响的电压幅值变化量也越小。且在传感器的测量盲区内,电压输出信号将会受到偏置磁场与电压输出波形叠加的影响,这两种因素都会导致传感器检测失效。该研究结果为多磁环位移传感器磁环的选型及减小传感器磁环间的测量盲区提供理论基础。     

基于自联想神经网络的传感器故障诊断

提出一种基于自联想神经网络(AANN)的新算法用于系统中传感器故障诊断。阐述了AANN的结构和算法。具体说明了搜寻2个故障传感器和恢复信号的方法。用改进的AANN诊断有噪声情况下传感器跳变故障并恢复信号。本方法有易实现、结构简单的优点,仿真结果表明:本方法是可行的。     

纸质传感器在点伪钞机中的应用

对点伪钞机识别假币的关键器件─纸质传感器（近紫外线传感器）进行了研究，有效地解决了识别假币的三个关键问题，即传感器的响应速度、灵敏度及温漂问题，提高了点伪钞机识别假币的准确性。     

附着式轧制力传感器及其零点校准

为实现轧制力传感器的快速安装,将附着式传感器安装于轧钢机机架立柱中性层上,通过测量机架立柱中性层上的应变,间接获取轧制力信息。为克服系统零点漂移对测量精度的影响,用数字电位器结合微处理器组成智能零点校准电路,智能识别零点漂移信号,并控制数字电位器进行实时零点校准,从而使系统的测量精度达到了1%FS的实用要求。     

Sensitivity Comparison of Surface Plasmon Resonance and Plasmon-Waveguide Resonance Biosensors

Plasmon-waveguide resonance (PWR) sensors are particularly useful for the investigation of biomolecular interactions with or within lipid bilayer membranes. Many studies demonstrated their ability to provide unique qualitative information, but the evaluation of their sensitivity as compared to other surface plasmon resonance (SPR) sensors has not been broadly investigated. We report here a comprehensive sensitivity comparison of SPR and PWR biosensors for the p-polarized light component. The sensitivity of five different biosensor designs to changes in refractive index, thickness and mass are determined and discussed. Although numerical simulations show an increase of the electric field intensity by 30-35% and the penetration depth by four times in PWR, the waveguide-based method is 0.5-8-fold less sensitive than conventional SPR in all considered analytical parameters. The experimental results also suggest that the increase in the penetration depth in PWR is made at the expense of the surface sensitivity. The physical and structural reasons for PWR sensor limitations are discussed and a general viewpoint for designing more efficient SPR sensors based on dielectric slab waveguides is provided.     

环境电磁污染监测仪设计

以AVR单片机Atmegai6L为控制器,以磁敏传感器HMCI052L为测量元件,组成环境电磁污染监测系统。二维磁敏传感器HMCI052L可差分输出,通过运算放大器LMV358放大差分信号,利用单片机Atmega 16L的模数转换器转换成数字信号,最后在LCDI602上显示出测量结果。利用磁阻芯片特有的置位／复位功能,有效地消除了因温度漂移和电路参数漂移等共模信号造成的误差,提高了磁敏传感器的灵敏度。通过硬件和软件设计,该系统能够测量磁场参数,测量精度可达到0．6raG．。     

一种压力传感器的零点补偿电路

从压力传感器温度补偿问题出发,通过三种电阻桥零点输出补偿方法的温度误差对比,提出一种恒压供电的新型电阻桥零点输出补偿方法,主要特点是调节压力传感器(零点输出10mV以上)零点输出为零时,不会影响压力传感器的温度漂移,且较传统的电阻桥零点补偿方法,压力传感器的温度误差小的优点.     

基于最小二乘支持向量机的硅压阻式传感器温度补偿

针对硅压阻式传感器灵敏度和零点温度漂移大、硬件补偿电路效果不佳的问题,提出最小二乘支持向量机方法对其温度漂移进行补偿。首先分析了经硬件补偿后的硅压阻式传感器的温度漂移特性,在整个检测范围内选取均匀分布的温度、压力数据作为模型输入,经预处理后对输出数值进行训练,并运用网格搜索法和交叉确认法优化模型的惩罚因子和正则化参数,建立了传感器温度补偿模型。实验结果表明,基于最小二乘支持向量机的温度补偿算法在0~100℃温度范围内把传感器输出综合精度从3.2%FS提高到0.25%FS,进一步提高了传感器的精度和温度使用范围,具有较高的实用价值。