船载海水重金属元素现场自动分析仪系统设计

【作者】 刘大龙；

【导师】 王平；

【作者基本信息】 浙江大学 ， 生物医学工程， 2004， 硕士

【摘要】 本文描述了用于海水中痕量重金属的在线分析的检测仪器的硬件和仪器固件的设计和实现。仪器使用多种测量技术(硫属玻璃电极，差分脉冲溶出伏安法和光寻址电位传感器)联用测量九种重金属元素。对于不同的测量技术，仪器中集成了用于测量电极的多通道高精度开路电压测量系统和用于溶出伏安法测量的多路电化学测量系统，以及用于测量光寻址电位传感器的锁相放大器。 针对不同的测量技术，我们提出了不同的解决方案。对于硫属玻璃电极，我们设计了以高精度的ΣΔADC为核心，配以高输入阻抗低噪声的前置放大器和低漏电流多路模拟开关的多路精密电极测量系统。对于微分脉冲伏安溶出测量，我们使用高精度高速SARADC和低偏置电流运放构成微电流采样系统，使用高精度DAC和高速大电流缓冲放大器设计了恒电位计，并与微控制器共通组成电化学测量系统。对于光寻址电位传感器，我们设计了以高精度调制／解调器件和数字频率合成器件为核心的模拟锁相放大器。仪器中均编写了相应的功能固件来完成特定功能，包括从简单的电压采样到复杂的电化学扫描过程。所有的子系统均运行相同的终端通讯协议，我们自行设计并称之为FlexLynx的协议，这种基于串行口物理设备的协议提供数据包组装，复杂数据校验和超时重传等机制保证可靠的数据传输。主机通过PC端的动态链接库可以完全控制目标仪器和获取采集数据。 仪器内嵌软件可控制仪器自动完成全部测量过程，为全自动在线测量提供完善解决方案。本仪器具全自动测量，适合现场检测，可扩展性好，可靠性高等特点。我们对完成的样机进行了性能测试，包括电化学系统的电流测量分辨率测试、环回扫描、恒压源输出稳定性测试，电极测量系统的测量有效位数测试。对锁相放大器做了基于电路微模型的滤波器参数仿真和同步整流原理仿真。测试结果表明仪器的硬件指标达到了我们的要求。 目前我们在进行仪器整体联合调试，测量系统已经可以全自动完成所有进样，测试，废液排除和清洗过程。我们的下一阶段的任务是仪器的定量测试和现场应用。更多还原

【Abstract】 The paper describes hardware and firmware implementations of the analytical instrument used to detect trace heavy metal in seawater. Multiple measurement techniques (chalcogenide ion selective electrode, differential pulse stripping voltammetry, light addressable potential sensor) have been combined to detect nine kinds of heavy metal. The instrument is integrated with a multi-channel high precision open circuit potential measurement system for the ion selective electrode and a potentiostat used in voltammetry, an analog lock-in amplifier is also presented to measure the response of light addressable potential sensor. With the embedded firmware, the instrument can perform the entire analysis automatically, thus provide a perfect solution for fully automatic on-line analysis.We have designed different measurement instruments according to the methods. The instrument used to measure electrode is a high precision multi-channel system constructed with a IAADC as the core and high input impedance amplifier and low input current multiplexer. The Electro-chemical measurement system used to perform DPSV measurement is constructed with two parts, a low-current measurement system consists of low input bias current operational amplifier and a high resolution SAR ADC and a potentialstat consists of high resolution DAC and high current buffer amplifier. The core of the Lock-in amplifier used to measure response of LAPS consists of a high precision modulator/demodulator and DDS as signal generator. A standardized communication protocol is running on all instruments, which is built by ourselves and has the code name of FlexLynx, it provide complex functions like data frame generation, data integrity check and time-out retransmission, so that data maintain its integrity while exchanging between PC and instruments.The instrument features full automatic measurement, wonderful extensibility and high reliability. The prototype has been assembled and fully checked , test results show it’s hardware performance can satisfy our project in all aspects.更多还原