以往我(wo)們經常從用戶使(shi)用儀表(biao)(biao)的角度，討論如(ru)何提高儀表(biao)(biao)的測量精(jing)度，例如(ru)從安裝維護(hu)調試這幾(ji)當面。今(jin)天我(wo)們將(jiang)從廠家制(zhi)造儀表(biao)(biao)的角度，來分析如(ru)何提高儀表(biao)(biao)的精(jing)度，本文我(wo)們將(jiang)重(zhong)點介紹一種(zhong)數據采集方(fang)法，這種(zhong)方(fang)法對提高儀表(biao)(biao)的測量精(jing)度和(he)響應速度有重(zhong)要的意(yi)義(yi)。

今天要分(fen)享(xiang)的(de)數(shu)據采集(ji)處理方式(shi)，是(shi)采用低功(gong)耗CPU，采用CPU自帶的(de)AD模(mo)塊(kuai)、DMA模(mo)塊(kuai)、定時器模(mo)塊(kuai)。采集(ji)波形時，使用TA定時器開始計時，開始AD轉(zhuan)換，AD轉(zhuan)換完(wan)成(cheng)后，啟動DMA傳(chuan)輸(shu)數(shu)據。

（圖(tu)源網絡(luo)）

首先是(shi)粗(cu)采(cai)(cai)樣(yang)(yang)(yang)，以比(bi)較低的(de)(de)(de)(de)(de)采(cai)(cai)樣(yang)(yang)(yang)率(lv)對原(yuan)始(shi)(shi)回波(bo)(bo)(bo)信(xin)號進(jin)(jin)行(xing)采(cai)(cai)樣(yang)(yang)(yang)，使用定時(shi)(shi)器達到25K時(shi)(shi)間(jian)(jian)(jian)產生(sheng)中斷(duan)信(xin)號啟動AD轉換，AD轉換完成(cheng)中斷(duan)標(biao)志(zhi)觸發DMA傳(chuan)(chuan)輸數據(ju)(ju)，以及(ji)RAM里面的(de)(de)(de)(de)(de)DMACPU信(xin)息到域(yu)，當DMA傳(chuan)(chuan)輸的(de)(de)(de)(de)(de)數據(ju)(ju)量(liang)達到1000個(ge)時(shi)(shi)，DMA中斷(duan)完成(cheng)數據(ju)(ju)傳(chuan)(chuan)輸，完成(cheng)對原(yuan)始(shi)(shi)回波(bo)(bo)(bo)的(de)(de)(de)(de)(de)粗(cu)采(cai)(cai)樣(yang)(yang)(yang)，給出(chu)數據(ju)(ju)處理標(biao)志(zhi)，CPU對數據(ju)(ju)進(jin)(jin)行(xing)處理，產生(sheng)虛(xu)假回波(bo)(bo)(bo)，計算(suan)(suan)回波(bo)(bo)(bo)曲線，確定起(qi)點(dian)(dian)(dian)位(wei)置(zhi)(zhi)和(he)真實有(you)效(xiao)(xiao)(xiao)回波(bo)(bo)(bo)位(wei)置(zhi)(zhi)，計算(suan)(suan)起(qi)始(shi)(shi)點(dian)(dian)(dian)和(he)有(you)效(xiao)(xiao)(xiao)波(bo)(bo)(bo)形位(wei)置(zhi)(zhi)所需的(de)(de)(de)(de)(de)延(yan)(yan)(yan)遲(chi)時(shi)(shi)間(jian)(jian)(jian)。其次精采(cai)(cai)起(qi)點(dian)(dian)(dian)位(wei)置(zhi)(zhi)，即以較高(gao)(gao)的(de)(de)(de)(de)(de)采(cai)(cai)樣(yang)(yang)(yang)頻率(lv)對原(yuan)始(shi)(shi)回波(bo)(bo)(bo)信(xin)號的(de)(de)(de)(de)(de)起(qi)點(dian)(dian)(dian)位(wei)置(zhi)(zhi)進(jin)(jin)行(xing)采(cai)(cai)樣(yang)(yang)(yang)，根(gen)據(ju)(ju)粗(cu)采(cai)(cai)樣(yang)(yang)(yang)時(shi)(shi)計算(suan)(suan)的(de)(de)(de)(de)(de)延(yan)(yan)(yan)遲(chi)時(shi)(shi)間(jian)(jian)(jian)，延(yan)(yan)(yan)遲(chi)時(shi)(shi)間(jian)(jian)(jian)在(zai)前，延(yan)(yan)(yan)遲(chi)時(shi)(shi)間(jian)(jian)(jian)在(zai)上，控(kong)制(zhi)AD、時(shi)(shi)序(xu)TA、DMA模(mo)塊(kuai)(kuai)得分接近起(qi)點(dian)(dian)(dian)80個(ge)點(dian)(dian)(dian)，采(cai)(cai)樣(yang)(yang)(yang)頻率(lv)較高(gao)(gao)。精采(cai)(cai)的(de)(de)(de)(de)(de)有(you)效(xiao)(xiao)(xiao)波(bo)(bo)(bo)形位(wei)置(zhi)(zhi)，即以較高(gao)(gao)的(de)(de)(de)(de)(de)采(cai)(cai)樣(yang)(yang)(yang)頻率(lv)對原(yuan)始(shi)(shi)回波(bo)(bo)(bo)信(xin)號的(de)(de)(de)(de)(de)有(you)效(xiao)(xiao)(xiao)波(bo)(bo)(bo)形位(wei)置(zhi)(zhi)進(jin)(jin)行(xing)采(cai)(cai)樣(yang)(yang)(yang)。時(shi)(shi)間(jian)(jian)(jian)選擇計算(suan)(suan)出(chu)的(de)(de)(de)(de)(de)延(yan)(yan)(yan)時(shi)(shi)時(shi)(shi)間(jian)(jian)(jian)先延(yan)(yan)(yan)時(shi)(shi)，延(yan)(yan)(yan)時(shi)(shi)時(shi)(shi)間(jian)(jian)(jian)結束后，控(kong)制(zhi)AD、定時(shi)(shi)器TA、DMA模(mo)塊(kuai)(kuai)在(zai)采(cai)(cai)樣(yang)(yang)(yang)頻率(lv)較高(gao)(gao)的(de)(de)(de)(de)(de)有(you)效(xiao)(xiao)(xiao)波(bo)(bo)(bo)形位(wei)置(zhi)(zhi)附近打(da)80個(ge)點(dian)(dian)(dian)。采(cai)(cai)集完成(cheng)后，設置(zhi)(zhi)數據(ju)(ju)計算(suan)(suan)標(biao)志(zhi)，開始(shi)(shi)計算(suan)(suan)。最后是(shi)數據(ju)(ju)計算(suan)(suan)，根(gen)據(ju)(ju)起(qi)始(shi)(shi)點(dian)(dian)(dian)、有(you)效(xiao)(xiao)(xiao)波(bo)(bo)(bo)形和(he)累計延(yan)(yan)(yan)遲(chi)時(shi)(shi)間(jian)(jian)(jian)，據(ju)(ju)此計算(suan)(suan)出(chu)準確的(de)(de)(de)(de)(de)起(qi)始(shi)(shi)點(dian)(dian)(dian)位(wei)置(zhi)(zhi)和(he)物(wu)料的(de)(de)(de)(de)(de)反(fan)射點(dian)(dian)(dian)位(wei)置(zhi)(zhi)，反(fan)射點(dian)(dian)(dian)位(wei)置(zhi)(zhi)與起(qi)始(shi)(shi)點(dian)(dian)(dian)位(wei)置(zhi)(zhi)之差為對應的(de)(de)(de)(de)(de)時(shi)(shi)差，反(fan)射距離，然后相應地(di)采(cai)(cai)樣(yang)(yang)(yang)頻率(lv)計算(suan)(suan)實際液位(wei)。

綜上所述，通過(guo)(guo)粗采(cai)樣確定有效(xiao)信(xin)號(hao)空間(jian)的(de)大(da)致位置，此(ci)時(shi)精度(du)較(jiao)低，然后(hou)通過(guo)(guo)高(gao)采(cai)樣頻(pin)率(lv)僅采(cai)集這部分駐波圖案，并進行計(ji)算(suan)過(guo)(guo)程(cheng)。在采(cai)集數據量(liang)不增(zeng)加太(tai)多的(de)基礎上提高(gao)了儀器的(de)測量(liang)精度(du)。總的(de)來說使(shi)用粗采(cai)精采(cai)的(de)這種方傳之后(hou)，減(jian)小了CPU的(de)計(ji)算(suan)任務量(liang)，大(da)大(da)提高(gao)了儀表(biao)的(de)響應(ying)速度(du)和測量(liang)精度(du)。