【正文】 tages of small size, high reliability, low price which made it very suitable to be used in industries of intelligent instrument and real time control . The operating interface of system is shown in Figure 2. Number at upper right corner shows the default or userdefined gas concentration value, number at upper left corner shows detected gas concentration value. One alarm lamp is equipped. All functions are controlled by keys arranged on the control panel, including POWER key, RESET key, DATA COLLECTION key. Other keys including ten number keys, ADJUST VALUE key and ENTER key are used to change threshold values. Basic operating procedures are as follows: Firstly press POWER key, the system initialized. Press DATA COLLECTION key, LED at upper right corner displays the threshold value 。它可以用于實(shí)時(shí)甲烷氣體濃度監(jiān)測(cè)。 串行通信模塊，信號(hào)控制器發(fā)送到主機(jī)計(jì)算機(jī)上通過(guò) RS485，和 MAX485是用于轉(zhuǎn)換電壓。當(dāng)它被暴露可燃?xì)怏w，測(cè)量元件電阻增大，輸出通 過(guò)測(cè)量電橋電壓參數(shù)，參數(shù)的電壓成正比的氣體濃度值。所有的功能通過(guò)設(shè)置控制面板上的按鍵控制，包括電源鍵，復(fù)位鍵，數(shù)據(jù)采集的關(guān)鍵。軟件調(diào)試和硬件仿真上述系統(tǒng)也實(shí)現(xiàn)在同一時(shí)間。 圖 3. 主控制單元 和信號(hào)放大電路 在氣體檢測(cè)系統(tǒng)設(shè)計(jì)的一個(gè)關(guān)鍵問(wèn)題是如何選擇的氣體傳感器。 圖 5. 信號(hào)放大電路 A / D轉(zhuǎn)換器模塊 如圖 6所示，該模塊由多路 CD4051，采樣保持器 lf389， A / D轉(zhuǎn)換器 AD574A [ 12 ]和并行 I/O 芯片 8255A作為核心的一部分， AD574A是一個(gè) 12位的逐次逼近 A/D轉(zhuǎn)換器芯片三的狀態(tài)緩沖區(qū)，其轉(zhuǎn)換時(shí)間約為 25μS. AD574A能夠直接連接到單片沒(méi)有額外的接口邏輯電路，內(nèi)置高精度的參考功率電源和時(shí)鐘電路，無(wú)需外部時(shí)鐘源 AD574A能夠正常運(yùn)行參考電源。我們需要三個(gè)存儲(chǔ)單元存儲(chǔ)這些數(shù)據(jù)是因?yàn)樗麄?24位二進(jìn)制數(shù)據(jù)格式。 User can customized threshold value by press ADJUST VALUE key and ten number keys, then press ENTER to confirm the change. System starts to detect gas concentration and display these parameters on upper left LED area, at meantime transmit realtime data by RS485 to host puter above ground. 3 Hardware System Design of Gas Detection System The Hardware architecture of system mainly including main control unit, sensors and signal amplifier circuit, A/D converter module, soundlight alarming circuit, keyboard and display module, serialmunication module. Main Control Unit Featured by high integration level, small size and low prices, Single chip microputer has been widely used in a broad range of industrial applications including process controlling, data collection, electromechanical integration, intelligent instrument, household appliances and work technology, and significantly improved the degree of technology and automation. Two factors are taken into account here in chip selecting, first one is antiinterference ability, increase the interferences in SCM application systems, so the SCM must have highresistance to outside interference。 5個(gè)結(jié)論 在這項(xiàng)研究中，一個(gè)智能氣體檢測(cè)系統(tǒng)。采用相反的方向連接的方法， PB口和 8155 PC端口（ 2）連接到鍵盤的行和列電路電路分別。 MC112氣體檢測(cè)器利用催化燃燒原理的兩個(gè)臂；橋是由測(cè)量與補(bǔ)償元件對(duì)。報(bào)警燈的設(shè)置。 關(guān)鍵詞：數(shù)據(jù)采集，傳感器 ,串行通信 ,單片機(jī)。常見(jiàn)的氣 體傳感器的半導(dǎo)體金屬氧 化物如氧化錫，鋅 coxide，鈦氧化物和鋁氧化物。 圖 6. A/D轉(zhuǎn)換器模塊 傳統(tǒng)的液晶顯示模塊是不適合在這個(gè)系統(tǒng)中由于工作環(huán)境主要是在黑暗的礦井隧道深。接下來(lái)，系統(tǒng)會(huì)將這些二進(jìn)制格式的數(shù)據(jù)轉(zhuǎn)換成二進(jìn)制編碼的十進(jìn)制格式，通過(guò)調(diào)用一個(gè)子程序三字節(jié)的二進(jìn)制編碼的十進(jìn)制。 second one is the performanceprice ratio of the the aforementioned factors, we adopted the AT89S52 developed by ATMELas main control unit, and the final scheme of main control circuit consists of AT89S52, timer and reset circuit [8,9]. As shown in figure Sensor Selection A crucial issue in gas detecting system design is