A novel solid state non-dispersive infrared CO2 gas sensor compatible with wireless and portable deployment

Area of Science:

• Optoelectronics
• Gas Sensing Technology
• Infrared Spectroscopy

Background:

• Non-dispersive infrared (NDIR) sensors are crucial for monitoring carbon dioxide (CO2) levels.
• Existing NDIR sensors often face limitations in terms of cost, power consumption, and operational lifespan.
• The development of robust and efficient light sources and detectors is key to advancing NDIR technology.

Purpose of the Study:

• To develop and evaluate a novel mid-infrared light emitting diode (LED) and photodiode (PD) pair for NDIR CO2 sensing.
• To demonstrate the performance advantages of this LED/PD combination in terms of speed, longevity, power, and cost.
• To assess the suitability of the developed sensor for widespread deployment in various monitoring applications.

Main Methods:

• Fabrication of a novel mid-infrared LED and PD light source/detector combination.
• Integration of the LED/PD pair into a non-dispersive infrared (NDIR) carbon dioxide gas sensor.
• Characterization of sensor performance, including stabilization time, longevity, power consumption, accuracy, noise, temperature effects, and cross-sensitivity.
• Evaluation of different pathlength variants for measurement range flexibility.
• Comparison with existing NDIR sensor technologies utilizing thermal or pyroelectric sources/detectors.
• Assessment of compatibility with energy harvesting strategies.

Main Results:

• The developed LED/PD based NDIR sensor exhibits a fast stabilization time of approximately 1 second.
• Achieved longevity exceeds 15 years with low power consumption, enabling extended battery or energy-harvested operation.
• Demonstrated accuracy and noise performance suitable for demanding applications.
• Two pathlength variants cover measurement ranges from ambient to 100% CO2 concentration.
• The semiconductor-based fabrication and injection-molded optics facilitate low-cost, high-volume manufacturing.

Conclusions:

• The novel mid-infrared LED/PD combination offers a viable and cost-effective solution for NDIR CO2 sensing.
• The sensor's performance characteristics are well-suited for "fit and forget" wireless deployments in building management, transportation, horticulture, and portable safety/medical devices.
• Low power consumption and long lifespan make it ideal for battery-powered and energy-harvesting systems.
• The manufacturing approach supports scalable and economical production for broad market adoption.