Development and Field Deployment of a Compact Dual-Range Infrared Carbon Dioxide Sensor System

A dual-range mid-infrared carbon dioxide (CO₂) sensor is developed with temperature and humidity compensation functionalities. Using the same optical path, the sensor employs dual-channel signal processing circuits to achieve measurements across two detection ranges of 200-3000 parts-per-million (ppm) (low concentration range) and 8-25% (high concentration range), respectively. The developed sensor, with a compact size of 8.5 × 5.5 × 3.5 cm³, shows a good linear response, with fitting goodness R² = 0.99942 for the low range and R² = 0.9993 for the high range. Under environmental conditions of 20 °C temperature and 30% relative humidity and with an averaging time of 1 s, the limits of detection are 0.15 ppm for the low range and 32.4 ppm for the high range, respectively. A temperature and humidity compensation scheme based on multiple linear regression is proposed to mitigate the impact of environmental temperature and humidity changes. The experimental results demonstrate that the relative error after compensation is reduced from 21% to 0.87%. Indoor and outdoor CO₂ measurements are performed to validate the good characteristics of the sensor system.