Research And Development Of Non-dispersive Infrared CO₂ Gas Concentration Analyzer

With the continuous development of science and technology, also people's concerning about greenhouse gas rising, there is a growing demand for CO2 gas concentration monitoring and control in many aspects of industrial production and daily life. At present, the methods of CO2 gas concentration analysis are electrochemical method, electrical method, chromatography, infrared absorption method and so on. The infrared absorption method with the merits of high accuracy, good stability, fast response, small size equipment and a long life is now becoming the new development orientation of CO2 gas concentration measurement field.This paper applied the least-squares curve fitting algorithm also modulated light source and a new sensor into the design of CO2 gas concentration detection instrument which was based on the analysis of infrared absorption theory and Lamber-Beer law. It has designed a new kind of dual-channel non-dispersive infrared CO2 gas concentration detection instrument. This paper focuses on the hardware and software design of modulated light source, gas chamber, sensors and signal acquisition, processing circuitry. This paper used the least-squares curve fitting algorithm to establish the mathematical model of infrared CO2 gas concentration detector which was based on a comprehensive analysis of error production and an in-depth study of its temperature characteristics. A series of experiments was carried out to provide data sources for the improving of infrared CO2 gas concentration detector, including: temperature characteristics experiment, which provides a reliable data for the establishment of the mathematical model and temperature compensation; modeling results curve fitting experiments to test and verify the accuracy of the mathematical model; experiment of stability character, which can verify the functioning degree of the detector in inhibiting the drift of measurement result. The infrared CO2 gas concentration detector designed in this paper was completed; all function and expected performance index were achieved. The detector has the mea- surement range of 0% -3.02%; repeating error of 0.0172%; relative error of 0.95% and the response time less than 1.5s. The results of the experiments showed that the detector can reduce the temperature influence of the measurement effectively and ensure the me- asurement accuracy in its working conditions. This detector has the distinguishing char- acteristics of high precision, good stability, small size, rapid response and so on.