研究智能氣體檢測系統(tǒng)外文翻譯-其他專業(yè)(編輯修改稿)
2025-02-24 03:01 本頁面
【文章內(nèi)容簡介】 n, 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。 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 how to select gas sensors. Common gassensors are metal oxide semiconductor such as tin oxide, zin coxide, titanium oxide andaluminum oxide. Problems encountered with these sensors are lack of flexibility, poor response times and operated at elevated temperature [10]. A new method of ch4 detecting based on infrared techniques was presented in recent years, but it is still in progress and much work should be done before it can be applied to solve the practice problems [11]. This system adopted catalytic bustion type gas sensor MC112 developed by SUNSTAR group to measure the gas (ch4) concentration. Figure 4 shows the outside view and internal circuit of MC112, table 1 lists the main technology parameters of MC112. MC112 gas detector exploits catalytic bustion principle。 the twoarm bridge is prised of measure and pensate ponents pairs. When it is exposed to bustible gases, measure ponents resistance RS increased and transmit output voltage parameter through measuring bridge, the voltage parameter is directly proportional to the gas concentration value. The pensate ponent works as temperature pensation and reference. Main features of MC112 include good repeatability, work stably, reliability, linear output voltage, and quick response. The mine safety rules stated that if methane gas concentration exceeds 1%, safety system should make an alert, if gas concentration exceeds 2%, all people must evacuate immediately. Since the detecting range of MC112 for low concentration methane is 0%2%. Fig. 4. Outside view Signal Amplifier Circuit It is necessary to amplify the weak electrical signal detected by MC112 (1% gas concentration fluctuation will result in 16mv voltage change). The system adopted AD623 developed by AD Company as the high performance instrumentation amplifier. It has many merits: (1) output with 312v single supply (2) easy to modify signal gain though an external resistor, it will be act as a unit gain without external resistor and signal gain can reach to 1000 with an external resistor。 (3)low power consumption, largescale operation voltage, good linearity, good thermal stability and high reliability. The schematic diagram of signal amplifier circuit is shown in figure 5. A/D Converter Module As shown in Figure 6, this module consists of multiplexer CD4051, sampling holder LF389, A/D converter AD574A[12] and parallel I/O chip 8255A. As a core part, AD574A is a 1
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