温度传感器信号采集外文文献翻译

温度传感器信号采集外文文献及翻译

温度传感器信号采集外文文献及翻译

(文档含英文原文和中文翻译)

Research of Intelligent Gas Detecting System

Detecting system in this paper adopts single-chip microcomputer as control computer;the overall schematic diagram of system is shown in Figure 1. The reason for selectingsingle-chip microcomputer as a control core is that it possesses advantages of smallsize, high reliability, low price which made it very suitable to be used in industries ofintelligent instrument and real time control .The operating interface of system is shown in Figure 1.

Number at upper right cornershows the default or user-defined gas concentration value, number at upper left cornershows detected gas concentration value. One alarm lamp is equipped. All functions arecontrolled by keys arranged on the control panel, including POWER key, RESET key,DATA COLLECTION key. Other keys including ten number keys, ADJUST VALUEkey and ENTER key are used to change threshold values

温度传感器信号采集外文文献及翻译

Fig.1 The operating interface of system

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 1.00;

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 upperleft LED area, at meantime transmit real-time data by RS-485 to host computerabove ground.

The Hardware architecture of system mainly including main control unit, sensors andsignal amplifier circuit, A/D converter module, sound-light alarming circuit, keyboardand display module, serial-communication module.

Featured by high integration level, small size and low prices, Single chip microcomputer has been widely used in a broad range of industrial applications including process controlling, data collection, electromechanical integration, intelligent instrument,household appliances and network technology, and significantly improved the degree of technology and automation.

温度传感器信号采集外文文献及翻译

Fig.2 Main control unit

Two factors are taken into account here in chip selecting, first one is anti-interferenceability, increase the interferences in SCM application systems, so the SCM must have highresistance to outside interference; second one is the performance-price ratio of the SCM.Considering the aforementioned factors, we adopted the AT89S52 developed by ATMELas main control unit, and the final scheme of main control circuit consists ofAT89S52, timer and reset circuit .

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. 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 .

This system adopted catalytic combustion 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 combustion principle; the two-arm bridge is comprised of measure and compensate components pairs. When it is

温度传感器信号采集外文文献及翻译

exposed to combustible gases, measure components resistance RS increased and transmit output voltage parameter through measuring bridge, the voltage parameter is directly proportional to the gas concentration value. The compensate component works as temperature compensation 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. 3 Outside view

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 3-12v 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, large-scale operation voltage, good linearity, good thermal stability and high reliability. The schematic diagram of signal amplifier circuit is shown in figure 4.

温度传感器信号采集外文文献及翻译

Fig.4 Signal amplifier circuit

As shown in Figure 5, this module consists of multiplexer CD4051, sampling holder LF389, A/D converter AD574A and parallel I/O chip 8255A. As a core part, AD574A is a 12-bit successive-approximation A/D converter chip with three-state buffer, its conversion time is about 25μs. AD574A can directly connected to AT89S52 without additional interface logic circuit, with internal high accuracy reference power supply and clock circuit, AD574A can operate normally without external clock sourceand reference power supply.

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