Nondispersive Infrared Carbon Dioxide Sensors with Ray-Guided Multi-Reflector and Dome Collector for Electrical and Environmental Monitoring

A compact-type nondispersive infrared (NDIR) carbon dioxide (CO2) sensor featuring a novel optical sensing cell (OSC) is designed and developed using ray-guided multi-reflector (RGMR) and dome collector (DC) techniques. A comprehensive design model is established using COMSOL Multiphysics, TracePro, Multisim, and Python computational techniques to evaluate and analyze the sensor configuration and performance. A signal conditioner is also created to maximize the amplification gain while minimizing the noise and thermal drift. The ray-guiding feature, multi-pass feature, and ray-focusing feature enabled simultaneously by the novel RGMR-DC OSC effectively enhance the optical path length per unit volume (OPLV), relative ray intensity (RRI), and RRI consistency at maximum allowable placement error (RRIC), reaching high levels of 4.4 cm/cm3, 2.86%, and 96.2% at a reasonably small OSC volume of 25 cm3, respectively. Three sensor samples are fabricated, and their performances are evaluated experimentally to explore the detection sensitivity, resolution, and stability. The measured detection sensitivity and resolution are 56.8-20.0 μV/ppm and 0.26-0.74 ppm for 400-5,000 ppm CO2 concentration at 25°C, while the hourly fluctuation and weekly drift are 1.30 and 1.96 ppm at 400 ppm CO2 concentration and 25±3°C temperature, respectively.