The Design Of Detection System For Indoor CO Gas Concentration

With the development of science and technology, the heavy use of new materials andnew energy inevitably brings negative effects to the living environment of human beings,especially the generating of many kinds of harmful gas which seriously influence thesafety and health of human. People spend the longest time in the indoor environment. Thecondition of Indoor Air Quality (IAQ) is related to human’s health so that monitoring thecondition of IAQ is significant. The price of the gas detection instrument in the currentmarket is generally higher that hinder widespread use of the instrument. This article isaimed at designing a portable gas detection system which is easy to use, perfect offunction and lower cost. It could apply to detecting gas concentration in the indoorenvironment, thereby decreasing accidents and hazards.This article starts with chip selecting type of system and expands from two coremodules that are electrochemical gas sensor and micro-computer of STC89C52. Thesystem chooses carbon monoxide to be the detection target which is the most common andharmful in the indoor environment. Gas sensitive components of gas sensor react with gasmolecules in the air. It leads the sensor to extract concentration of information and outputweak electrical signals. The signals are transformed into Binary digital signal by theamplifying circuit and A/D conversion circuit and then input into micro-computer. Thesoftware procedure in micro-computer can carry on processing the signals, and thencontrol of following equipment to generate sound and light alter and display test data andother functions after that. After startup, we can choose data detection model or upload datamodel. In the testing progress, when detection value is greater than threshold value, thesystem produces sound and light alter and displays real time data; when detection value isless than threshold value, it just displays detection data. Historical data could be uploadedto PC via micro-computer serial port. Users could query and analyze detection data bymeans of PC interface which is developed by VC++. This function makes the system morehumanized and can be convenient for analyzing the change of indoor environment.