阻抗谱测量系统的设计

论述了单片机控制的阻抗谱测量系统的设计和实现方法,采用直接数字频率合成器(DDS)产生同步的正交信号源,采用双差分减法器实现了阻抗到电压的转换,并利用双相锁定放大器提高了抗干扰性能。由于测量通道的增益会随频率而变化,采取了校准措施,并利用可编程的开关电容低通滤波器,以加速测量。仿真实验结果表明:加入高斯白噪声,信号噪声比为-10~10 dB。频率范围为1Hz~100 kHz,阻抗幅值和相位测量的相对误差小于4%。     

基于AD5933的葡萄糖水溶液阻抗分析系统

介绍了基于AD5933的阻抗检测原理和软硬件实现。系统设计采用阻抗测量芯片AD5933,以低功耗高性能处理器STC89C52单片机作为控制器。该检测仪采用AD5933中的数字频率合成器(DDS)产生激励信号,施加在待测阻抗上,ADC采集相应信号并送到片内DFT模块进行数字处理,测量结果通过I2C送至单片机,再由单片机与计算机上位机通信,计算机显示该阻抗值。该仪器能实现电阻、电容、电感阻抗快速、准确地测量,经实验验证,阻抗幅值和相位测量的相对误差较小,(电阻阻抗平均偏差为0.041 1,相位平均偏差为0.152°)。葡萄糖水溶液浓度与阻抗呈线性相关,相关系数大于0.99。     

I2C总线接口的FPGA实现研究

该文详细阐述了I2C总线接口的结构、工作原理,提出了复杂时序电路状态机嵌套的设计思想,并给出了基于VerilogHDL的I2C接口电路的描述。     

一种功率测量专用数字信号处理器的实时仿真系统

介绍一种功率测量专用数字信号处理器的实时仿真系统,其仿真速度高、实时性强、且成本低廉,具备了软件模拟不可比拟的优越性。使用该仿真系统,可以确定目标芯片的一些重要参数、以及算法实现中的常数;同时,该仿真系统的系统分割、优化,也对目标芯片的设计有着重要的指导意义。     

用I2C总线实现AD7416的多点温控系统

详细介绍新型数字式温度传感器AD7416的功能、结构和特性参数,并给出其在多路循环温湿度检测控制仪中的应用实例.通过实践可知,AD7416测温范围宽、准确度高,相比其它数字式温度传感器有连接及编程简单的优点,具有推广使用价值.     

用电阻抗测量的人体成分分析方法研究

为了实现人体生理成分的测量及定量分析,本文基于人体电阻抗信号设计了一套以AD5933芯片为基础的硬件扩展电路和以PSO-ELM预测算法为核心的采集及分析系统,能够实时采集并分析人体电阻抗信号,将不同频率下的人体电阻抗信号加以处理及分析,从而实现人体生理成分的测量。在此设计中完成了对系统的整体调试并对人体电阻抗等相关数据进行采集处理。分析结果表明,该系统运行稳定,准确率较高,符合预期的设计要求。     

一种基于I~2C总线驱动的锅炉温度测量系统设计

提出了一种基于I2C总线驱动的锅炉温度测量系统,介绍了系统的结构、硬件设计和软件开发。系统以单片机为核心,选用了I2C总线器件PCF8591实现A/D转换,及I2C总线接口的E2PROM芯片AT24C01存储温度值。系统的数据交换都是基于I2C总线的通信标准,该设计方案结构简单、易于扩展,提高了锅炉温度测量的精度和抗干扰能力,具有实际应用价值。     

基于FPGA的同步数据采集处理系统的设计与实现

针对目前多通道数据采集系统的局限,以EP1K50系列的FPGA为核心控制模块,AD7656为模数转化芯片实现了精度为16位、最大采集速率为250kS/s的同步模拟信号采集系统,采用Flash存储采集到的数据,且可以通过PC104总线将数据传输到上位机。给出了系统的电路设计、关键模块逻辑图以及软件流程图。     

基于I2C总线的多处理器测控系统的研究

为解决嵌入式应用在工业控制中存在的问题,提出一种利用I²C总线进行测控的应用方案。根据I²C的多主多从、实现简单、器件多样等特性,在多个处理器上进行编程,实现了一种方便、灵活的测控系统。结果表明,系统采集数据和控制设备的实时性得到了很大提高。     

交流阻抗法测定锂离子电池正极材料的导电率

采用交流阻抗法测定了3种锂离子电池正极材料LiCoO2,LiMn2O4和LiFePO4的电子导电率、离子导电率和材料电导率.结果表明,LiCoO2材料的电导率较高,含有聚阴离子基团LiFePO4材料的电子电导率和离子电导率均较低.     

Method for flow measurement in microfluidic channels based on electrical impedance spectroscopy

We have developed and characterized two novel micro flow sensors based on measuring the electrical impedance of the interface between the flowing liquid and metallic electrodes embedded on the channel walls. These flow sensors are very simple to fabricate and use, are extremely compact and can easily be integrated into most microfluidic systems. One of these devices is a micropore with two tantalum/platinum electrodes on its edges; the other is a micro channel with two tantalum/platinum electrodes placed perpendicular to the channel on its walls. In both sensors the flow rate is measured via the electrical impedance between the two metallic electrodes, which is the impedance of two metal–liquid junctions in series. The dependency of the metal–liquid junction impedance on the flow rate of the liquid has been studied. The effects of different parameters on the sensor’s outputs and its noise behavior are investigated. Design guidelines are extracted and applied to achieve highly sensitive micro flow sensors with low noise.     

Direct measurement of electric double layer in a nanochannel by electrical impedance spectroscopy

The ion distribution and physical behavior induced by applying an electric field to a nano-interfacial space are very important for investigating electric double layers (EDLs) in very confined spaces. We perform direct measurements of an EDL in a nanochannel by electrical impedance spectroscopy to experimentally evaluate the EDL thickness dependence on the ion density and the channel width. To this end, we developed a nanofluidic device consisting of a pair of sensing electrodes with a nanochannel between them. The measurement electrodes are completely embedded in a substrate to generate a uniform electric field and to provide a flat surface that can easily be used to seal the nanochannel. Using this device, we found that the EDL on one electrode expands with decreasing ion concentration and eventually merges with the EDL on the opposite electrode so that the nanochannel becomes completely filled with the EDL. The trend observed for the EDL width agrees well with that predicted by theory for the Debye length. These results provide valuable insight into the physical ionic structure in nanochannels, which will improve impedance-based electrical sensing and electrokinetic applications.     

An integrated banking network system

In 1974, the Barclays Bank computer network consisted of three separate computer centres, each serving 600 – 900 branches. In the event of a major catastrophe at any one centre, it would not have been possible to service the branches connected to it. The paper describes the Barclays Integrated Network System, which was developed to insure against such a situation. Further facilities that will be offered by the system when it is completed are also described.     

用于评估皮肤渗透能力的无创皮肤阻抗测量系统

设计了基于AD5933的无创皮肤阻抗测量系统,用来评估皮肤渗透能力,提高经皮给药、提取组织液目标物的效率。系统利用二电极比例法,并采用时钟频率切换、量程自动切换和软件校准补偿等技术,实现了对低频皮肤阻抗的测量。基于电穿孔法进行促渗透处理前后的皮肤对系统进行了阻抗测量实验验证。结果表明:该系统可用于对皮肤渗透性的表征,可给人体生理生化检测相关的可穿戴设备参数调节提供依据。     

基于V/I转换电路与锁相放大器的磁阻抗测量系统

为了实现GMI传感器的低成本及便携式应用,一种新型的GMI传感器检测系统被提出并研究,新型GMI传感器检测系统由信号源、V/I转换电路及锁相放大器构成。在1 MHz到10 MHz的激励信号频率范围内,利用新型检测系统对NiFe/Cu/NiFe三明治结构的GMI传感器进行了测量,并且与惠普公司4194A型阻抗分析仪在相同条件下的测量结果进行了比对分析,在频率为6 MHz时比较结果显示该系统的误差范围小于1.5%。     

An integrated circuit layout design system

An integrated circuit layout design system is presented. The system is effectively combined with a combinatorial optimization technique and man/machine interaction. This optimization technique allows wiring and placement of components to be determined simultaneously. By means of a c.r.t. display, the layout design of an integrated circuit chip is finally improved.     

一个集成化软件过程度量系统的设计与实现*

为了使企业度量活动满足企业各层级角色的度量需求,提出了一个建立企业集成化软件过程度量体系的方法,给出了一个度量模型及其典型应用,描述了一个企业集成化软件过程度量系统的体系结构及功能。在系统支持下,企业度量活动的效率得到了有效提升。