基于CAV424的电容式液位传感器信号调理电路研究

介绍了一种电容式液位传感器信号调理电路设计的新方法,通过利用单片的电容／电压信号转换芯片CAV424实现了对电容量的简单、准确测量,同时通过单片机进行智能补偿以实现测量的高精度。该传感器具有测量精度高、可靠性好和较高的性价比等优点。     

微小电容检测及报警电路的设计

设计了一种基于CAV424和AM402的微小电容检测及报警电路,该电路可以将微小的电容信号转换成4～20mA的电流输出,介绍了该电路的内部结构和工作原理,并通过实验验证了该电路的实用性。     

测量围护结构含水率的同面散射场式电容传感器设计

目前常用的测量含水率的方法有微波法、红外线法和电容法.由于基于电容法的传感器具有分辨力高、响应速度快、体积小、结构简单等优点,被广泛应用.针对围护结构含水率测试深度的要求和测试特点,本文通过仿真和实验,对同面电容传感器探头的结构尺寸进行了优化设计,并采取了保护电极以提高其抗干扰能力;运用改进的充放电电容检测电路,设计出一种测量围护结构含水率的新型同面散射场式电容传感器,该传感器具有宽范围的测试深度和较高的测试灵敏度.     

油品含水率的测量技术展望

油品含水率的测量方法很多,主要在原油含水率在线测量方面应用比较广泛,在满足测量要求的情况下,许多方法也可以用于其他油品含水率的测量。传     

基于V/T变换的电容传感器新型电容测量电路

提出了一种基于V／T变换的用于电容传感器的电容测量电路。它将被测微小电容变化量转换成时间信号并由单片机进行处理，电路结构简单，电路中没有影响测量稳定性和产生零点漂移的元器件，大幅度地降低了测量过程中的噪声。     

高精度微小电容测量电路的研制

介绍了一种数字电路与模拟电路相结合的测量电路，可用于微小电容的测量。实验结果表明，电路的线性度、分辨率和稳定性等性能指标均达到了测量要求。     

油品含水率多点实时监测系统的研制

提出了润滑系统油品含水率多点在线实时监测系统的实现方法,设计了基于变介电常数式电容传感器的润滑油品含水率变送器,根据高速线材厂液压循环润滑系统的特点,利用组态王软件,实现对液压系统的润滑油含水率进行多点实时监测.通过在高速线材厂液压循环系统的使用证明,该系统能够准确、快速地测出润滑油品的含水率并及时报警,从而避免了润滑失效所带来的潜在危害.     

基于多极板电容传感器测量原油含水率的研究

设计了测量原油含水率的多极板式电容传感器及测量电路;建立了多极板式电容传感器测量原油含水率的数学模型,得到了原油含水率变化量与多极板式电容传感器等效电容变化量之间的函数关系.进行了五极板式电容传感器和单极板式电容传感器测量油水混合物含水率的对比实验.实验结果表明采用五极板式电容传感器测量油水混合物的含水率,相对于采用单极板式电容传感器测量油水混合物的含水率的测量精度有大幅度的提高;而且采用五极板式电容传感器测量油水混合物的含水率,无论是在低含水率端还是在高含水率端其测量结果都比较稳定.     

利用直流数字电压测量电容的电路

本主要介绍一种由振荡器，有源滤波器，线性整流器组成的检测电路，该电路与直流数字电压表配合使用，可实现对电容量的测量。     

重新评价基于充放电原理的微电容测量电路

基于充放电原理的电容测量电路是目前微电容测量中广泛采用的一种测量电路，其最大的特点是电路具有抗分布电容特性且简单实用。本文对基于充放电原理的微电容测量电路进行了深入研究，利用微分方程的数值解法，通过计算机仿真得到了各种参数对电路的影响。     

基于均匀设计及非线性偏最小二乘法的非闭合电极ECT传感器参数优化设计

提出了一种非闭合电极电容层析成像(ECT)传感器结构参数的优化方法.采用均匀设计结合非线性偏最小二乘(NPLS)回归,提取传感器结构参数(电极极板的宽度 L、绝缘外壳的壁厚δ1.、屏蔽罩与绝缘外壳间距δ2及绝缘外壳材料的相对介电常数ε)与待优化指标(敏感场的均匀度及灵敏度指标p1、最大与最小电容的比值 K)间的函数关系,建立相应的优化目标泛函,通过对优化目标泛函的求解,最终获得传感器结构参数的最优值.并以 10 电极非闭合电极 ECT 传感器为研究对象,进行了结构参数的优化设计,根据优化结果设计制作了非闭合电极 ECT 传感器,对其成像进行了仿真与实测.结果表明,参数优化后的传感器图像重建质量优于未优化的传感器.     

基于涡流检测信号的金属曲面距离测量方法研究

为提高曲面试件的涡流测距精度,提出一种基于涡流信号差值的测距修正方法.该方法通过研究不锈钢平板试件与曲面试件涡流信号的不同,拟合计算出曲面涡流信号和平面涡流信号之间差值与曲面试件曲率的定量关系.利用这一函数关系,对不同曲率试件的测量结果进行补偿,可修正由于试件存在曲面造成的测量误差.通过实验进行可行性验证,对平板试件与...     

A signal processing technique for measurement of multimode waveguide signals: An application to monitoring of reaction bonding in silicon nitride

A system that uses ultrasonic techniques to monitor the reaction bonding of silicon nitride is described. Reaction bonding of silicon nitride takes place in a nitrogen atmosphere at temperatures up to 1400°C. As with many sensors used in hostile environments, it is difficult to design the ultrasonic sensor in a way that provides optimal clarity of the signal. The sensing system must be designed within the physical limitations on access to the furnace. Ultrasonic probes that accommodate limited access to the silicon nitride sample have been designed and ultrasonic signals acquired during processing, albeit with significant noise and complexity in the signal. Signal processing techniques are used which make it possible to measure changes in phase velocity and attenuation during reaction bonding. Because of variability in the measured velocity and attenuation, the method of signal processing presented is applicable to those cases where it is not possible to redesign the probe for optimal clarity of the ultrasonic signal. This technique demonstrates the potential to perform measurements using signals that would have been considered intractable in the past. Data obtained from ultrasonic monitoring are suitable for use as input to a manufacturing process control feedback loop.     

一种改进的唤醒信号能量检测算法及其应用研究

为了减少水下无线传感器网络的功耗,在notch滤波器算法原理基础上,结合帕斯瓦尔定理和子带能量目标检测算法分析环境噪声,得到了检测门限随环境噪声变化的唤醒信号检测算法,进行了理论分析和仿真。在微功耗处理器上实现了该算法并讨论了其在水下无线传感器网络的应用。试验证明该算法可以灵活调度网络中的各个节点状态,降低了传感器网络的功耗。     

基于激光位移传感器的手持式轮对尺寸测量仪设计

针对轨道交通轮对几何尺寸检测需求不断增加、检测工具自动化水平低、检测精度低的现状,设计一种基于一维激光位移传感器的手持式轮对尺寸测量仪。该设备以STM32F407芯片作为微控制器,通过控制直线步进电机,配合激光位移传感器实现对轮对廓形二维点云数据的采集,采用基于中值误差与连续度调整权值的平滑算法对点云数据预处理,采用基于轮对轮廓特征的廓形匹配实现轮对尺寸参数的计算。该仪器对车轮轮廓进行全面记录和质量评估,试验证明,该设备在保持较高测量精度的情况下,同时具有高效测量、长时间工作等特点。     

Statistical modeling of the radio-frequency signal for partially- and fully-developed speckle based on a generalized gaussian model with application to echocardiography

We have shown previously that the statistics of the radio-frequency (RF) signals may be faithfully modeled through the so-called K(RF) distribution, in situations ranging from fully to partially-developed speckle. We demonstrate in this paper that the generalized Gaussian provides a reliable and computationally convenient approximation of the K(RF). The performance of the parameters estimators for the two distributions is evaluated and compared in terms of their bias and variance through numerical simulations. This framework is applied to the modeling of echocardiographic data. The ability of the generalized Gaussian to model RF signals from cardiac tissues (myocardium) and blood regions is demonstrated on data acquired in vivo.     

An electrochemical sensor based on Pt/g-C3N4/polyaniline nanocomposite for detection of Hg2+

The synthesis of Pt/g-C₃N₄/polyaniline nanocomposites (Pt/g-C₃N₄/PAn NCs) via the direct reduction of Pt (II) in the presence of L-cysteine as the reducing agent is presented in this study. X-ray diffraction analysis showed that the Pt cations were reduced to metallic Pt in the presence of L-cysteine. Field emission scanning electron microscope images confirmed a low agglomeration of metallic Pt when synthesized in the presence of g-C₃N₄. Electrochemical impedance spectroscopy results showed that the low conductivity of g-C₃N₄ is compensated with the presence of polyaniline (PAn). A glassy carbon electrode modified with the Pt/g-C₃N₄/PAn NCs showed high selectivity and sensitivity for the detection of Hg²⁺. The presence of active sites in the g-C₃N₄ and PAn enhanced the adsorption of Hg²⁺. The voltammetric response was linear in the concentration range of 1–500 nM Hg²⁺, with the detection limit of 0.014 nM (at S/N = 3).     

大视场星敏感器矢量观测在轨检校模型

针对大视场星敏感器的在轨标定问题,提出了一种基于矢量观测的检校新模型。将3个罗德里格参数代替欧拉角,作为外方位参数与畸变参数、内方位参数一起求解,简化了运算。采用仿真星图分析了模型的性能,结果表明,该模型较采用欧拉角的传统标定模型精度更高,在星点位置噪声方差为0.05 pixels的情况下,仍能准确解算出星敏感器参数,其星内角距的统计偏差为0.483″,x、y方向的残差绝对均值分别为0.019 pixels、0.016 pixels,且算法的参数设置简单,无需计算初值。将检校模型应用于ZY-3号卫星星敏感器的检校,结果表明模型可以有效提高检校的精度。建议在实际应用中采用精度更高的星点中心计算算法。     

An application of Markov chains to predict the evolution of performance indicators based on pavement historical data

One of the main awareness for a road infrastructures manager is to increase its efficiency under limited resources. Pavement Management Systems aim, at last, to support road administrations in the decision-making process regarding its management policy and long-term strategies for maintenance and rehabilitation activities. While several road administrations are putting efforts in developing optimisation methodologies to enhance their decision making process, many still lack of data that allows the development of reliable prediction models for pavement performance. This is a key aspect to develop and test decision-making methodologies. Although there are several prediction models available in the literature, their practical applications are often limited to the very specific network from which data were retrieved at first and to a specific performance indicator (PI). This paper presents a practical application of a Markov model to predict the evolution of five PIs – cracking, skid resistance, bearing capacity, longitudinal evenness and transverse evenness – and consequent combined PIs, using historical data from an extensive pavement database. The conversion for PIs is made through a standardisation procedure proposed by an European COST Action, which may be considered a reference classification system for road administrations. The presented model is intended to be an useful input for researchers and administrations willing to develop and test different optimisation approaches.