The Research On Infrared CO₂ Concentration Sensor System

With the continuous development of society economy, science and technology, variety of gas concentration sensors are applied in industry, agriculture,environment protection, and healthcare and so on. But at present there are still many shortcomings in these most gas sensors, for example, short service life, poor stability and low accuracy and so on. In order to resolve these shortcomings, this article takes CO2 as research gas, designs a concentration of CO2 gas sensor based on NDIR(Non-dispersive Infra-Red,NDIR), which is able to measure CO2 much more quickly, accuracy and stability.This article takes gas density sensor which is based on the dispersion of light infrared method(NDIR) as the object of study, elaborates in detail the domestic and foreign present research situationas, compared with other gas sensors, and summarizes the superiority of the infrared gas sensor. Then it introduces the spectral absorption principle, the infrared detection principle and the difference examination principle, has designed the system overall plan in this foundation. This article chooses the appropriate infrared source, infrared detector, concentrated cup, window piece and so on as the parts of the system, determines and designs the mechanism of the entire sensor system, the corresponding light driver circuits, the amplifying and filtering circuits, AD converter circuits and so on, compiles the control programs of the MCU and the receiving and processing program of the PC software.At last, this article analyses the fitting data with the Origin software through the experiment, finishes the calibration of the gas and the test of the accuracy,repeatability, stability and respond time of the sensor system, in the meantime,analyses the tolerance of the sensor system aiming at the entire gas. As we can see from the experiment results, this sensor system is able to measure the density of the gas correctly, quickly and stably.