【正文】 ent rate in the first. For security reasons, the methane concentration measurement, appear particularly on the above, the gas concentration detection problem, critical. This paper studied and designed a variety of gas concentration can be measured, and can alarm intelligent tester. The design scheme based on STC89C52 MCU, MQ3 alcohol concentration sensor, MQ4 methane concentration sensor. System circuit of the sensor output signals from the AD0832 as the core of the A / D conversion circuit after conditioning, through the singlechip microputer for data processing, LCD display by the alcohol concentration value. And the design of certain limits, overrun alarm. Limit value by the keys to adjust. Considering the SCM calculation ability is limited, to plex data processing, so singlechip system and PC system through the RS232 serial munication port interconnect, thereby SCM as the next bit machine data acquisition and control equipment, and the machine used PC do PC for plex data processing and the SCM control. This paper introduces the data acquisition subsystem, data processing and data display system and alarm circuit, SCM and PC munication hardware and software to achieve the design method and process. System for sampling locations beyond the prescribed specified gas concentrations, through sound and light alarm circuit to remind staff monitoring. At the same time, the operator for a specific alarm limit values can be set through the singlechip programming. Key words: alcohol oncentration sensor (MQ3), methane concentration sensor ( MC113), STC89C52, A/D converter,Dataelector (74HC4051), serial munication, RS232,VB。盡我所知，除文中特別加以標(biāo)注和致謝的地方外，不包含其他人或組織已經(jīng)發(fā)表或公布過的研究成果，也不包含我為獲得 及其它教育機(jī)構(gòu)的學(xué)位或?qū)W歷而使用過的材料。 作 者 簽 名： 日 期： 指導(dǎo)教師簽名： 日 期： 使用授權(quán)說明 本人完全了解 大學(xué)關(guān)于收集、保存、使用畢業(yè)設(shè)計(jì)（論文）的規(guī)定，即： 按照學(xué)校要求提交畢業(yè)設(shè)計(jì)（論文）的印刷本和電子版本；學(xué)校有權(quán)保存畢業(yè)設(shè)計(jì)（論文）的印刷本和電子版，并提供目錄檢索與閱覽服務(wù)；學(xué)?？梢圆捎糜坝　⒖s印、數(shù)字化或其它復(fù)制手段保存論文；在不以贏利為目的前提下，學(xué)?？梢怨颊撐牡牟糠只蛉?jī)?nèi)容。除了文中特別加以標(biāo)注引用的內(nèi)容外，本論文不包含任何其他個(gè)人或集體已經(jīng)發(fā)表或撰寫的成果 作品。本人完全意識(shí)到本聲明的法律后果由本人承擔(dān)。本人授權(quán) 大學(xué)可以將本學(xué)位論文的全部或部分內(nèi)容編入有關(guān)數(shù)據(jù)庫進(jìn)行檢索，可以采用影印、縮印或掃描等復(fù)制手段保存和匯編本學(xué)位論文。 作者 簽名： 日期： 年 月 日 導(dǎo)師簽名： 日期： 年 月 日 V 目錄 引言 ................................................................ 1 第 1 章 前言 ......................................................... 2 ......................................................................................... 2 國內(nèi)外氣體濃度檢測(cè)技術(shù)的發(fā)展現(xiàn)狀 .................................................................... 3 非光學(xué)分析法 .................................................................................................. 3 光學(xué)分析法 ...................................................................................................... 4 單片機(jī)與 PC 機(jī)串行通信研究背景和意義 ............................................................. 5 本氣體濃度測(cè)試儀的設(shè)計(jì)內(nèi)容 ............................................................................... 5 第 2 章 方案器件簡(jiǎn)介 ................................................. 6 MCU 簡(jiǎn)介 ............................................................................................................... 6 模數(shù)轉(zhuǎn)換器簡(jiǎn)介 .................................................................................................... 9 液晶顯示器的簡(jiǎn)介 ............................................................................................... 12 電源電 平轉(zhuǎn)換芯片（ TTL 電平轉(zhuǎn) RS232 電平） .................................................. 13 數(shù)據(jù)選擇器 ......................................................................................................... 13 第 3 章 串口通信基礎(chǔ)理論 ............................................ 14 兩種常用接口方式 .............................................................................................. 14 .并行接口 ............................................................................................................... 14 .串行接口 ............................................................................................................... 14 RS232 串行接口標(biāo)準(zhǔn) ........................................................................................... 15 VB 編程過程中使用到的 MSComm 控件 ............................................................ 16 . MSComm 控件處理通信的方式 ..................................................................... 16 ． MSComm 控件的主要屬性 ............................................................................ 16 第 4 章 總體方案設(shè)計(jì) ................................................ 18 STC89C52 MCU ..................................................................................................... 19 ADC0832 數(shù)模轉(zhuǎn)換 ............................................................................................... 19 LCD1602 液晶顯示 ................................................................................................ 19 單電源轉(zhuǎn)換芯片 MAX232 .................................................................................... 21 數(shù)據(jù)選擇器 74HC4051 ........................................................................................ 21 用于串口轉(zhuǎn) USB 的芯片 CP2102（實(shí)際使用） .................................................... 22 設(shè)計(jì)中使用到的軟件介紹 .................................................................................... 23 第 5 章 硬件設(shè)計(jì) .................................................... 25 最小系統(tǒng)的實(shí)現(xiàn) .................................................................................................. 25 信號(hào)采集電路 ..................................................................................................... 27 MC113 及其測(cè)量電路的特點(diǎn) ........................................................................ 27 VI MQ3特點(diǎn)及其測(cè)量電路原理 ........................................................................ 29 關(guān)于氣體濃度單位的說明 ............................................................................ 32 A/D 轉(zhuǎn)換設(shè)計(jì) .......................................................................................................