船载海水重金属元素现场自动分析仪系统设计
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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。
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.
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。
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.
引文
[1] Tiina Petanen, Martin Romantschuk, Use of bioluminescent bacterial sensors as an alternative method for measuring heavy metals in soil extracts, Analytica Chimica Acta 456(2002) 55-61
[2] Yuri Vlasov, Andrey Legin, Alisa Rudnitskaya, Cross-sensitivity evaluation of chemical sensor for electronic tongue: determination of heavy metal ions, Sensors and Actuators B, vol.44, p.532-537, 1997.
[3] Flash In-System Programmable Peripherals For 8-Bit MCUs, ST Microelectronics Product Data Sheet, Product Name PSD81XF2
[4] Dan Harris, 80C32/PSD8XX Design Guide for PSDsoft 2000, Waferscale Integration, Inc. Application Note 064
[5] High-Speed Micro Memory Interface Timing, Dallas Semiconductor, App Note 89
[6] Memory Expansion with the High-Speed Microcontroller Family, Dallas Semiconductor, Application Note 81
[7] FET-Input, Low Power Instrumentation Amplifier, Burr-Brown Product Data sheet, Product Name INA121
[8] 24-Bit Analog-to-Digital Converter, Burr-Brown Corporation Product Datasheet, Literature Number SBAS034A
[9] Bonnie C. Baker, Synchronization of External Analog Multiplexers with Delta-Sigma A/D Converters, Burr-Brown Corporation Application Bulletin, Literature Number SBAA013
[10] Bonnie C. Baker, How to get 23 bits of effective resolution from your 24-bit converter, Burr-Brown Corporation Application Bulletin, Literature Number sbaa017
[11] Miaochen Wu, Interfacing The ADS1210 With An 8xC51 MicroController, Burr-Brown Corporation Application Bulletin, Literature Number SBAA010
[12] Sigma-Delta ADCs and DACs, Analog Device Inc Technical Library. Literature Number AN-283
[13] Using Sigma-Delta Converters-Patt 1 and, Analog Device Ine Technical Library. Literature Number AN388 and AN389
[14] 蒲国刚，袁倬斌，吴守国，电分析化学。中国科学技术大学出版社
[15] 方昉，韩清鹏，刘大龙 等，选择性电极和脉冲伏安法联用检测痕量重金属元素的电子舌研究，STC’03全国敏感技术和传感器学术交流会，北京，2003，11，16-18
[16] Combining an Amplifier with the BUF634, Burr-Brown Corporation Application Note, Literature Number sboa065
[17] Precision Switched Integrator Transimpedance Amplifier, Burr-Brown Corporation Product Data Sheet, Product Name IVC 102
[18] Bonnie C. Baker, Comparison of Noise Performance Between a FET Transimpedance Amplifier and Switched Integrator, Burr-Brown Corporation Application Bulletin, Literature Number sboa034
[19] Bruce Carter and L.P. Huelsman, Handbook of Operational Amplifier Active RC Networks, Texas Instruments Application Report, Literature Number SBOA093A
[20] Bruce Carter and Thomas R. Brown, Handbook of Operational Amplifier Applications, Texas Instruments Application Report, Literature Number SBOA092A
[21] Ron Mancini, Op Amps For Everyone, Texas Instruments Reference Guide, Literature Number SLOD006B
[22] Robert J. Widlar, Working with High Impedance Op Amps, National Semiconductor Application Note 241
[23] Tips for Using the ADS78xx Family of A/D Converters, Burr-Brown Corporation Application Bulletin, Literature Number SBAA003
[24] 门洪，王子，邹绍芳 等，基于PLD的硫系薄膜光寻址电位传感器的研究，仪表技术与传感器，投稿．
[25] Walt Jung and Moshe Gerstenhaber, Modem-Circuit Techniques Simplify Instrumentation Designs, Analog Device Inc Technical Library, Literature Number AN-307
[26] Moshe Gerstenhaber and Frank J. Ciarlone, Commutating Amp Multiplies Precisely, Analog Device Inc Technical Library, Literature Number AN308
[27] Steven W. Smith, The Scientist and Engineer's Guide to Digital Signal Processing, Second Edition, California Technical Publishing
[28] A Technical Tutorial on Digital Signal Synthesis, Analog Device, Inc, 1999
[29] Andrea Ghedi, The Lock in Modulation in Ultra Low Frequency Application.
[30] Jonathan Y. Stein, Digital Signal Processing: A Computer Science Perspective, John Wiley & Sons, Inc. Print ISBN 0-471-29546-9
[31] Andreas Chrysafis, Digital Sine-Wave Synthesis Using the DSP56001, Motorola Digital Signal Processing Division
[32] David Buchanan, Choosing DACs for Direct Digital Synthesis, Analog Device Application, Inc, Application Note 237
[33] Understanding and Using Cyclic Redundancy Checks with Dallas Semiconductor Button Products, Dallas Semiconductor, Application Note 27
[34] MGC Analog Designer Process Guide, Mentor Graphics Corporation Process Guide
[2] Yuri Vlasov, Andrey Legin, Alisa Rudnitskaya, Cross-sensitivity evaluation of chemical sensor for electronic tongue: determination of heavy metal ions, Sensors and Actuators B, vol.44, p.532-537, 1997.
[3] Flash In-System Programmable Peripherals For 8-Bit MCUs, ST Microelectronics Product Data Sheet, Product Name PSD81XF2
[4] Dan Harris, 80C32/PSD8XX Design Guide for PSDsoft 2000, Waferscale Integration, Inc. Application Note 064
[5] High-Speed Micro Memory Interface Timing, Dallas Semiconductor, App Note 89
[6] Memory Expansion with the High-Speed Microcontroller Family, Dallas Semiconductor, Application Note 81
[7] FET-Input, Low Power Instrumentation Amplifier, Burr-Brown Product Data sheet, Product Name INA121
[8] 24-Bit Analog-to-Digital Converter, Burr-Brown Corporation Product Datasheet, Literature Number SBAS034A
[9] Bonnie C. Baker, Synchronization of External Analog Multiplexers with Delta-Sigma A/D Converters, Burr-Brown Corporation Application Bulletin, Literature Number SBAA013
[10] Bonnie C. Baker, How to get 23 bits of effective resolution from your 24-bit converter, Burr-Brown Corporation Application Bulletin, Literature Number sbaa017
[11] Miaochen Wu, Interfacing The ADS1210 With An 8xC51 MicroController, Burr-Brown Corporation Application Bulletin, Literature Number SBAA010
[12] Sigma-Delta ADCs and DACs, Analog Device Inc Technical Library. Literature Number AN-283
[13] Using Sigma-Delta Converters-Patt 1 and, Analog Device Ine Technical Library. Literature Number AN388 and AN389
[14] 蒲国刚，袁倬斌，吴守国，电分析化学。中国科学技术大学出版社
[15] 方昉，韩清鹏，刘大龙 等，选择性电极和脉冲伏安法联用检测痕量重金属元素的电子舌研究，STC’03全国敏感技术和传感器学术交流会，北京，2003，11，16-18
[16] Combining an Amplifier with the BUF634, Burr-Brown Corporation Application Note, Literature Number sboa065
[17] Precision Switched Integrator Transimpedance Amplifier, Burr-Brown Corporation Product Data Sheet, Product Name IVC 102
[18] Bonnie C. Baker, Comparison of Noise Performance Between a FET Transimpedance Amplifier and Switched Integrator, Burr-Brown Corporation Application Bulletin, Literature Number sboa034
[19] Bruce Carter and L.P. Huelsman, Handbook of Operational Amplifier Active RC Networks, Texas Instruments Application Report, Literature Number SBOA093A
[20] Bruce Carter and Thomas R. Brown, Handbook of Operational Amplifier Applications, Texas Instruments Application Report, Literature Number SBOA092A
[21] Ron Mancini, Op Amps For Everyone, Texas Instruments Reference Guide, Literature Number SLOD006B
[22] Robert J. Widlar, Working with High Impedance Op Amps, National Semiconductor Application Note 241
[23] Tips for Using the ADS78xx Family of A/D Converters, Burr-Brown Corporation Application Bulletin, Literature Number SBAA003
[24] 门洪，王子，邹绍芳 等，基于PLD的硫系薄膜光寻址电位传感器的研究，仪表技术与传感器，投稿．
[25] Walt Jung and Moshe Gerstenhaber, Modem-Circuit Techniques Simplify Instrumentation Designs, Analog Device Inc Technical Library, Literature Number AN-307
[26] Moshe Gerstenhaber and Frank J. Ciarlone, Commutating Amp Multiplies Precisely, Analog Device Inc Technical Library, Literature Number AN308
[27] Steven W. Smith, The Scientist and Engineer's Guide to Digital Signal Processing, Second Edition, California Technical Publishing
[28] A Technical Tutorial on Digital Signal Synthesis, Analog Device, Inc, 1999
[29] Andrea Ghedi, The Lock in Modulation in Ultra Low Frequency Application.
[30] Jonathan Y. Stein, Digital Signal Processing: A Computer Science Perspective, John Wiley & Sons, Inc. Print ISBN 0-471-29546-9
[31] Andreas Chrysafis, Digital Sine-Wave Synthesis Using the DSP56001, Motorola Digital Signal Processing Division
[32] David Buchanan, Choosing DACs for Direct Digital Synthesis, Analog Device Application, Inc, Application Note 237
[33] Understanding and Using Cyclic Redundancy Checks with Dallas Semiconductor Button Products, Dallas Semiconductor, Application Note 27
[34] MGC Analog Designer Process Guide, Mentor Graphics Corporation Process Guide