激光粒度儀是一種最先進的、最具有廣泛發(fā)展前景的粒度測量儀器,，它的測量原理基于米氏(Mie)散射理論,。MIE散射理論是一個經(jīng)典的光散射理論，它最大的特點是可用于任何尺寸段顆粒的測量,，但它的計算相當復雜限制了數(shù)據(jù)處理速度及精度,。

　　DSP技術實現(xiàn)MIE散射算法有很多優(yōu)點：它是專為算法計算而設計的專用CPU，所以它運算速度很快,；與通用CPU相比它成本低,，所以有很好的性價比；而且它的體積小,，能實現(xiàn)儀器一體化等等優(yōu)點,。ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" 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title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM" title="ARM">ARM具有豐富的片上資源，適合嵌入式系統(tǒng)的開發(fā),，主要負責操作系統(tǒng)的運行,、任務管理和協(xié)調(diào)以及DSP的控制任務，外部可擴展多種外設,，如通用串口,、LCD顯示屏、以太網(wǎng)接口,。

　　1 系統(tǒng)總體設計及工作原理

　　1．1 激光粒度儀工作原理

　　激光粒度儀的組成框圖如圖1所示,。

 

　　激光粒度儀中的光電探測器采集顆粒在一定角度范圍內(nèi)的散射光來得到顆粒的粒徑分布信息。由于光電探測器處在傅里葉透鏡的焦平面上，因此探測器上的任一點都對應某一確定的散射角,。光電探測器陣列由一系列同心環(huán)帶組成,，每一環(huán)帶是一個獨立的探測器，能將投射到上面的散射光能線性地轉(zhuǎn)換成電壓,，然后送給采集卡,。該卡將電信號放大，再進行A／D轉(zhuǎn)換后送入計算機,，按事先編制的程序根據(jù)米氏散射理論進行數(shù)據(jù)處理,，把散射譜的空間分布反演為顆粒大小的分布。

　　1．2 電路系統(tǒng)的總體設計

　　激光粒度儀電路總體框圖如圖2所示,。采集電路采集到的數(shù)據(jù)經(jīng)過RS232串口傳輸給DSP,，經(jīng)過DSP的運算后，再把DSP處理后得到的結(jié)果數(shù)據(jù)RS232經(jīng)過串口傳輸給ARM處理器,，在ARM處理器的觸摸屏界面上顯示結(jié)果,。

　　2 電路系統(tǒng)具體設計方案

　　2．1 數(shù)據(jù)采集電路設計

　　粒度儀的光電探測器是用光電池做成多元環(huán)形，多元環(huán)形光電探測器接收散射光的光能量,，環(huán)形光電池把光能量轉(zhuǎn)換為光電流,。然后經(jīng)過電流電壓轉(zhuǎn)換器，把電流信號轉(zhuǎn)換為電壓信號,。再經(jīng)過放大電路放大,，然后輸入到A／D轉(zhuǎn)換器，將模擬信號轉(zhuǎn)換為數(shù)字信號,。然后把數(shù)字信號輸入到C805lF320單片機,，單片機然后再傳給DSP進行處理，如圖3所示,。

　　系統(tǒng)的硬件組成分為以下幾個部分：環(huán)形光電探測器,、數(shù)據(jù)選擇部分、電流電壓轉(zhuǎn)換部分,、運算放大部分,、模數(shù)轉(zhuǎn)換部分和中央單片機控制部分。

　?、倌M多路選擇器選用ADG506,，它精度高，為1mV,，抗干擾能力強,，功耗低，價格便宜,；

　?、陔娏麟妷恨D(zhuǎn)換電路有起濾波作用的電容及可調(diào)電阻,，有利于調(diào)整電路參數(shù)；

　?、蹫V波放大電路的二階Butterworth低通濾波器截止頻率為10Hz,，主要濾除工頻干擾；

　?、苣?shù)轉(zhuǎn)換電路采用的芯片是TLC2551,，此芯片是14位A／D，輸入電壓范圍為：O～5V,；理論采集精度可達0．3mV,，受實際測試條件所限制實際測試精度可達0．8mV；A／D轉(zhuǎn)換時間為10m,，采集速度很高,；此芯片抗干擾能力強，功耗低,，性價比高,；

　　⑤控制電路采用C8051F320作為采集電路的控制芯片,，它片上資源豐富,，主頻高可達25MHz，而且開發(fā)簡單,，性價比高,。單片機采集來的數(shù)據(jù)通過串口發(fā)送給DSP芯片。

　　2．2 DSP運算電路的設計

　　DSP作為一種用的數(shù)字信號處理器,，自從問世以來,，DSP就以數(shù)字器件特有的穩(wěn)定性,，可重復性,，可大規(guī)模集成，特別是可編程性和易于實現(xiàn)自適應處理的特點,，給數(shù)字信號處理的發(fā)展帶來了巨大的機遇,。

　　激光粒度儀的采集電路采集來的數(shù)據(jù)通過RS232串口傳送給DSP處理器，經(jīng)過DSP進行算法運算,，運算完成后再通過RS232串口傳送給嵌入式ARM處理器顯示結(jié)果,。原理框圖如下圖4所示：

 

　　①DSP芯片選用TMS320C5416,，TMS320C5416采用改進的哈佛結(jié)構,，具有以下優(yōu)點：具有高度并行性和專用硬件乘法器和加法器的CPU設計，芯片性能大大提高,；程序存儲器和數(shù)據(jù)存儲器是相互獨立的存儲器,，每個存儲器獨立編址，獨立訪問。本系統(tǒng)中設置了16路數(shù)據(jù)總線,，32路地址總線,，其余的為控制總線。

　?、诖?shù)據(jù)轉(zhuǎn)換采用的芯片為TLl6C752B,，此芯片有兩個串口控制器，控制器A和控制器B,。D00到D07為8位數(shù)據(jù)總線,，RXA和TXA與RXB和TXB分別為A口與B口的數(shù)據(jù)發(fā)送端口和數(shù)據(jù)接收端口。CSA和CSB分別為A口和B口的片選端口,。

　?、跼S232電平轉(zhuǎn)換電路，采用的電平轉(zhuǎn)換芯片為MAX3160它把3．3V的TTL電平轉(zhuǎn)換為RS232電平,。

　　2．3 ARM顯示電路的設計

　　三星公司開發(fā)的S3C2440A是一款以ARM920T為內(nèi)核的嵌入式微處理器,，它的最高工作頻率達433MHz，內(nèi)含3通道的異步串行口,，USB主,、從單元設備接口，攝像頭接口,，觸摸LCD／TFT控制器等眾多片上外設接口,。LCD屏TD035STED2為3．5英寸，屏幕分辨率為320×240,，能提供262K中色彩,。

　　2．4 PCB設計

　　PCB設計采用的設計軟件為Protel99，PCB設計的關鍵是：模擬電路部分要具有很好的抗干擾能力和高可靠性,。提高電路的抗干擾能力的方法有：①元器件布局要合理,；②布線要合理；③覆銅要合理,；④金屬殼接地屏蔽等,。

　　3 實驗結(jié)果分析

　　在完成電路系統(tǒng)設計的基礎上，進行激光粒度儀實驗,。在相同環(huán)境,、相同采集電路、相同Mie算法條件下,，分別用標準P4臺式機和DSP+ARM電路進行實驗,。實驗樣品采用滿足R-R單峰分布的粒徑范圍為O．1～100μm的碳酸鈣。

　　以上兩種方式分別連續(xù)20次測試,，相對于標準樣品,，實測d50誤差在±3％,，d10和d90誤差在±5％之內(nèi)，重復精度在±3％以內(nèi),，說明采集精度達到了儀器標準,。實驗驗證，此系統(tǒng)設計方案比標準P4機運算至少快10s,。

　　4 結(jié)束語

　　本文將DSP的高速處理能力和ARM得管理能力結(jié)合起來,，使整個系統(tǒng)在結(jié)構上獲得最大的靈活性。高性能DSP可以滿足運算性能方面的需要,，而ARM的可控性,。可以解決觸摸顯示采集結(jié)果,。同時減小了儀器體積,，提高了運算速度。