Design And Test Of The Infrared CO₂Gas Sensor Module

With the development of science and technology, the gas sensors have gradually comeinto people’s lives and the manufacture. Despite infrared gas sensors came out a little late,their advantages of high sensitivity, long life, low maintenance costs make them developrapidly. Infrared gas sensors make measurement in a non-contact way, and have nodangerous of pollution and explosion, so the infrared gas sensors have a huge advantage inthe measurement of some kinds of flammable gas, and have a broad application prospects.This thesis introduces the design and test process of an infrared gas sensing modulebased on a pair of commercial thermal emitter source and thermopile infrared detector. Thegas sensor module contains a infrared source, a gas chamber, a detector, an AD converter, anMCU and an LCD, etc., and can detect and display CO₂concentration in relatively stableenvironment. The module is an NDIR detection system for CO₂, and can simply be used forsome other gases’ detection with a little change, so the module can be used as a basic modelof infrared gas sensor.This thesis first introduces the development status of infrared gas sensors and thedirection of future development, and its advantage relative to other gas sensors. Then ttheoretical knowledge of infrared detection, spectral absorption principle Lambert-Beer’s lawas well as the principle of NDIR are given. The design process of hardware circuit andsoftware program are also introduced, with the hardware circuit diagram and programflowchart, problems and solutions in the design process are explained in detail. Finally,designing of vacuum testing chamber for sensor module is described and the measuredsignal data is processed and calibrated. The final results of data processing, and limit inexperiments, and the future improvement direction of are given out.