基于FPGA的溶液电化学阻抗谱测量系统设计

摘要

电化学阻抗谱是土壤及其溶液的一项重要电化学参数.基于直接数字合成DDS (Direct Digital Synthesis)技术和现场可编程门阵列FPGA(Field-Programmable Gate Array)器件设计了一套测量精度较高的溶液电化学阻抗谱EIS(Electrochemical Impedance Spectroscopy)测量系统.基于FPGA+数模转换器D/A(Digital-to-Analogue Converter)形成DDS子系统,其功能是输出频率连续可调的正弦波信号;基于FPGA+模数转换器A/D(Analogue-to-Digital Converter)形成数字信号处理DSP(Digital Signal Processing)子系统,其功能是获取被测物的频率响应.将二个子系统结合,获取反映电化学阻抗谱的奈奎斯特图,由此进一步获得溶液的欧姆电阻、电荷传递电阻和电极溶液界面双电层电容等电化学参数.结果表明,DDS和FGPA等现代电子技术的应用,为电化学参数的高精度测量提供了有效途径.%Electrochemical Impedance Spectroscopy(EIS)is an important electrochemical parameter of soil as well as its solution.A high precision measurement system of solution EIS is designed based on Direct Digital Synthesis(DDS)technology and field-programmable gate array(FPGA)device.DDS subsystem is formed based on FPGA+digital-to-analogue converter(D/A),whose function is to generate sine waves with a continuously adjustable frequencies,while the Digital Signal Processing(DSP)subsystem is built based on FPGA+analogue-to-digital converter(A/D),whose function is to obtain the frequency response of the measured object.Combination of both enables obtainment of the Nyquist diagram to reflect the EIS,thereby further,multiple electrochemical parameters,such as the ohmic resistance,charge transfer resistance and the dual-layered capacitance of the electrode-solution interface,become obtainable.The measurement results indicate that the modern electronic technologies'' application,such as DDS,FGPA,etc,provides an effective way for high-precision measurement of electrochemical parameters.