Development of a compact NDIR CO₂ gas sensor for harsh environments

We present a compact non-dispersive infrared (NDIR) gas sensor that can be adopted in high-moisture and low temperature environments. The NDIR gas sensor was formed by a Micro-Electro-Mechanical Systems (MEMS) emitter working at 400degree celsius with a broadband radiation spectrum, a MEMS thermopile detector that integrated with an optical filter, a compact gas-cell with high optical coupling efficiency of similar to 48 %, and an imbedded miniature thermostat. The footprint of the sensor is 24 mm x 8 mm x 8 mm (length x width x height), making it just 30 % of the size of conventional NDIR gas sensors with equivalent detection resolution, and its heat capability is around 7.29 J/K that promise a cost-effective thermoregulation. The sensor is capable of accurately detecting gas, such as Carbon dioxide, within a concentration range spanning from 0.5 % to 20 % with a reading error of +/- 0.1 % covering a working temperature from -20 degree celsius to 60 degree celsius. Because the sensor is equipped with a waterproof breathable film at the air hole, the sensor can operate in the humidity range from 0 to 100 %RH, and the maximum detection reading error is 0.1 % +/- 230 ppm. It is possible to be applied for both low temperature environments (e.g. food preservation cabinet, biological cabinet, etc) and high-moisture environments (e.g. greenhouse, humidity chambers, etc.).