Development and Application of CF4 Concentration Sensor Based on NDIR Principle

摘要

When designing gas chamber of infrared gas sensor, sometimes it is necessary to simulate the optical and fluid characteristics of the gas chamber. The purpose of optical simulation is to verify the influence of the 3D structure of the air chamber on the propagation of infrared light. During the simulation process, we can find the reflection, scattering and other physical phenomena of infrared light on the inner wall of the air chamber, and finally calculate the loss of infrared light in air chamber. Through this information, internal structure of the chamber can be further optimized. The simulation of fluid characteristics can also be called gas path simulation, which is to verify the influence of the 3D structure of the gas chamber on the diffusion of the measured gas in its interior. Through the simulation, a series of information about gas velocity and concentration distribution can be obtained, which can further optimize the structure of the gas chamber to ensure that the measured gas diffuses evenly and rapidly in the gas chamber. Firstly, the sensor concentration is calibrated at the different temperatures. The purpose of this step is to explore how much influence different temperatures will have on the output of the sensor, and to compensate temperature through the calibration data. In this paper, the five temperature points are selected for testing, which are −20°C, 0 °C, 10°C, 30 °C and 50°C. Keep the humidity at 25%. The test method is the same as the previous temperature test, in order to make the temperature inside the sensor chamber reach the required temperature faster.