基于FPGA的智能放大器的研究与实现

在许多检测仪表的设计和应用中,由于被测信号幅度变化范围大、频带宽,通常采用设置量程变换开关的方式对被测信号进行满量程放大以保证测量的精度,使得硬件结构复杂。为了实现测量的智能化, 设计了一种基于FPGA(Field Programmable Gate Array,现场可编程门阵列)的智能放大器,可以根据信号的变化相应调整放大器的增益、可对动态范围宽的输入信号用最佳增益对其进行放大,使得放大后输出信号落入设定的窗口范围之内。该放大器已应用于植物种苗磁电场复合诱导繁育控制系统中,运行结果表明,该设计参数精度高,可靠性强,方便实用。     

基于ARM嵌入式Linux的数据采集系统设计

针对传统数据采集系统的不足,文中介绍了一种基于ARM9的数据采集系统的设计原理和实现方法。以微处理器S3C2440A为核心,外扩高精度A/D芯片AD7606,设计了数据采集硬件电路,分析了AD7606和PWM定时器的基本工作原理,借助于移植的嵌入式Linux操作系统,实现了基于PWM和GPIO口的ADC驱动及相应的数据缓冲与软件抗干扰。测试结果表明,由ARM和Linux组成的数据采集系统具有操作方便、采集精度高和测量结果准确等优点。     

一种高性能机车速度数模转换装置的设计

为了适应铁路机车运行高性能、高可靠性要求,设计了一种高性能的机车速度数模转换装置。其作用是将机车轮对上的DF16型光电速度传感器传输来的数字脉冲信号,转换成0~6 V,0~20 mA两种模拟信号。该装置仅用2块IC芯片LM331和AD694及少量外围电路。其中LM331是将输入的数字脉冲信号转换成一定幅值的电压信号,然后由AD694将输出的电压信号转换成标准0~20 mA电流和0~6 V电压两种信号输出。该装置具有转换速度快、精度高(0.1%)、温度漂移小(100 ppm/℃)性能可靠等优点,是一款高性能的数模转换装置。     

基于双叉指电容和ZIGBEE的无线位移传感器

微位移测量技术可以实现微距环境下的位置感知与位移操作,其关键在于对位移的精密测量及实时传输。本研究基于平面双叉指电容和ZIGBEE技术设计了一种无线位移传感器系统,该系统由四部分组成：位移一电容转换模块,电容采集、发送节点,电容接收节点,基于VC＋＋开发的实时监控及结果显示软件。此外,下位机是基于ZIGBEE无线通信协议开发的。通过实验证明：系统具备6mm的测量范围,10um的分辨率,通信距离50m。     

智能电导率仪的设计

智能电导率仪采用交流测量法来测量电导率。正弦激励的产生是通过阻抗测试芯片AD5933来实现的。AD5933输出的正弦激励加在电导池的电极上,AD5933可以计算出溶液阻抗经过傅里叶变换后阻抗的实部R和虚部I(结果保存在AD5933的寄存器中),然后再计算出校准系数A,就可以通过单片机计算出溶液的真实阻抗,进而计算出溶液的电导率。温度补偿电路测量溶液温度,用于修正温度对测量带来的影响。     

基于DDS的可程控信号源的设计和实现

基于AD7008和AD7520芯片设计了一个可程控信号源,只需通过电脑设置发送控制命令参数,就能够产生频率和幅度符合要求的数字检测信号。详细介绍了该方案的软件和硬件的设计要点以及在调试中应注意的问题。调试结果及实际应用表明该信号源工作稳定,精度较高,频率、幅度控制都非常便利,在电子设备的电路板故障检测中起到了很好的作用。     

Recent advances in sample preparation techniques and methods of sulfonamides detection – A review

Sulfonamides (SAs) have been the most widely used antimicrobial drugs for more than 70 years, and their residues in foodstuffs and environmental samples pose serious health hazards. For this reason, sensitive and specific methods for the quantification of these compounds in numerous matrices have been developed. This review intends to provide an updated overview of the recent trends over the past five years in sample preparation techniques and methods for detecting SAs. Examples of the sample preparation techniques, including liquid–liquid and solid-phase extraction, dispersive liquid–liquid microextraction and QuEChERS, are given. Different methods of detecting the SAs present in food and feed and in environmental, pharmaceutical and biological samples are discussed.     

Miniaturized electrochemical system for cholinesterase inhibitor detection

The utility of a simple, low-cost detection platform for label-free electrochemical characterization of acetylcholinesterase (AChE) inhibition is demonstrated as a potential tool for screening of small-molecule therapeutic agents for Alzheimer's disease (AD). Technique validation was performed against the standard Ellman's colorimetric assay using the clinically established cholinesterase inhibitor (ChEI), Donepezil (Aricept^®). Electrochemical measurements were obtained by differential pulse voltammetry (DPV) performed using a portable potentiostat system for detection of the enzymatic product, thiocholine (TCh), by direct oxidation on unmodified gold screen-printed electrodes. The IC₅₀ profiles for Donepezil measured in vitro were found to be comparable between both colorimetric and electrochemical detection methods for the analysis of purified human erythrocyte-derived AChE (28 ± 7 nM by DPV; 26 ± 8 nM by Ellman's method). The selectivity of this unmodified electrode system was compared to a range of biological sulfur-containing compounds including cysteine, homocysteine, glutathione and methionine as well as ascorbic acid. Preliminary studies also demonstrated the potential applicability of this electrochemical technique for the analysis of Donepezil in crude cholinesterase samples from anterior cortex homogenates of C57BL/6J mice.     

基于AD7896的瞬时峰值电压测量仪

文中介绍了一款基于AD7896的瞬时峰值电压测量仪的设计.峰值检测是示波器中数据采集的重要方法,优于取样方式和平均方式.采用单片机控制方式,通过对峰值检测仪电路的整体框架的设计,给出了硬件电路各个单元模块的设计原理图,结合硬件设计,得到了软件设计的整体流程图以及中断函数流程图,仪器通过测试,简单易行,测试精度较高.