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I对无公害蔬菜生长环境的检测仪器的设计摘要蔬菜是最为重要的日常食物，对维持人体正常生理功能和增进健康具有不可替代的作用。随着现代工业迅速发展以及化肥、农药等农用物资的大量施用，蔬菜产地环境质量和其品质受到严重影响。射线探测器的能量分辨本领是能量色散X荧光分析实现高灵敏度多元素分析的关键。本文将具有高能量分辨率的电致冷SI-PIN半导体探测器应用于携带式X荧光仪，并设计、研制了与探测器相配套的电子线路单元和应用软件。通过最佳“源—样—探”几何参数论证，设计了基于同位素激发源的“对称边源”激发装置，有效提高X荧光探测的“峰背比”，进一步提高分析灵敏度;设计并制作了“无变压器式高压偏置电源”和“开关型温控致冷电源”，提高系统信噪比并降低了静态功耗。本设计是在深入了解单片机原理的基础上进行的。整个系统的设计符合环境监测仪器的基本要求。在缺乏试验条件的实际情况下，对系统关键参数进行了分析和整定。这对提高作物品质，进一步推广无公害蔬菜种植、促进农业的可持续发展具有重要意义。关键词：单片机，无公害蔬菜，土壤环境，X射线荧光分析，数据采集IIDESIGNOFTHEENVIRONMENTALMEASUREMENTDEVICETOTHEGROWTHOFPOLLUTION-FREEVEGETABLESABSTRACTVegetablesarenecessaryfoodinpeople'sdailylife,whichareadvantageoustopeople'sphysiologicalfunctionsandhealth.Withthedevelopmentsofmodemindustry,andtheusingofalargenumberofchemicfertilizersandpesticidemadethequalityofvegetablesandtheenvironmentofvegetablesbasesarebecomingworse.AstheenergyresolutionabilityforX-raydetectorissoimportantforhighsensitivemulti-elementanalysisusingEnergy-dispersiveX-rayFluorescence(EDXRF)method.TheSI-PINtypethermoelectricallycooledsemiconductordetectorisadaptedinaportableXRFanalyzer.TherelatedelectronicsunitsforSI-PINdetectorandtheapplicationsoftwarearedesignedanddeveloped.Aftertheoptimizationgeometryparametersofsource-sample-detectoriscalculatedanddiscussed,anisotopeexcitationsourcebasedBalanceSidesstructureexcitationsourcedeviceisdesigned.Thisschemeisfoundouttobeeffectiveforimprovingthepeak-to-backgroundradioofXRF.Andthedetectingsensitivityisimprovedaswell;Transformer-lesshighvoltagebiascircuitandtemperaturefeedbackself-adjustablevoltageswitchingregulatorforelectric-cooleraredeveloped.Thesecircuitscanimprovetheperformanceofsignal-to-noiseradio,reliability,andreducepowerconsumptionoftheentiresystem.Thedesignisbasedonthein-depthunderstandingofthebasicprincipleofMCU(MicroControllerUnit).Thedesignofthewholesystemofenvironmentalmonitoringequipmentisinlinewiththebasicrequirements.Intheabsenceoftheactualexperimentalconditions,thekeyparametersofthesystemproposedsettingtherightapproach.Thisdesignismeaningfultoimprovethequalityoffarmcrops,furtherpromotepollution-freevegetablesandkeepingagriculturalsustainabledevelopment.Keywords:MCU(MicroControllerUnit)，pollution-freevegetables，soilenvironmental，XRF(X-rayFluorescenceanalysis)，dataacquisitionIII目录1绪论-------------------------------------------------------------------------------------------------1-1.1土壤中有毒元素的来源-----------------------------------------------------------------1-1.2影响土壤中有害元素有效性的因素--------------------------------------------------2-1.3土壤中有害元素对人的危害-----------------------------------------------------------3-1.4本文背景-----------------------------------------------------------------------------------4-2论文主要任务和意义----------------------------------------------------------------------------6-2.1现场X荧光分析技术与仪器的研究现状-------------------------------------------6-2.1.1国外研究现状----------------------------------------------------------------------6-2.1.2国内研究现状----------------------------------------------------------------------8-2.2对X荧光探测系统的技术要求-------------------------------------------------------9-2.3论文选题及研究意义--------------------------------------------------------------------9-2.4论文的主要任务------------------------------------------------------------------------10-3基本原理及整体设计方案-----------------------------------------------------------------------113.1X荧光分析的基本原理----------------------------------------------------------------11-3.2信号放大调理电路的原理------------------------------------------------------------12-3.3数据处理单元的原理------------------------------------------------------------------13-3.3.1复位电路--------------------------------------------------------------------------16-3.3.2外部时钟电路--------------------------------------------------------------------17-3.3.3驱动电路--------------------------------------------------------------------------18-4无公害蔬菜生长环境检测仪硬件系统-------------------------------------------------------204.1探测器选择------------------------------------------------------------------------------19-4.1.1X射线荧光探测器--------------------------------------------------------------19-4.1.2激发源的选择--------------------------------------------------------------------21-4.1.3前端结构的选择-----------------------------------------------------------------22-4.1.4激发源在前端的布置-----------------------------------------------------------23-4.2信号处理电路的设计------------------------------------------------------------------24-4.2.1成型放大电路--------------------------------------------------------------------24-4.2.2脉冲调理电路--------------------------------------------------------------------25-4.2.3甄别及A/D装换器触发电路-------------------------------------------------26-IV4.3单片机外围电路设计------------------------------------------------------------------27-4.3.1键盘的选择-----------------------------------------------------------------------27-4.3.2显示单元的设计-----------------------------------------------------------------28-4.3.3A/D转换单元在系统中的位置-----------------------------------------------30-4.4系统工作条件的保障------------------------------------------------------------------32-4.4.1高