Low power NDIR CO2 sensor based on CMOS IR emitter for boiler applications

In this paper we demonstrate the use of a CMOS infra-red emitter in a low power Non Dispersive Infra Red (NDIR) based carbon dioxide sensor for application in domestic boilers. Compared to conventional micro-bulbs as IR wideband sources, CMOS IR emitters offer several advantages: They are faster, smaller, have lower power consumption and can have integrated circuitry. The emitter is a 1.16 mm × 1.06 mm chip with an integrated FET drive and consists of a tungsten heater fabricated in a CMOS process followed by Deep Reactive Ion Etching (DRIE) to form a thin membrane to reduce power consumption. The NDIR sensor consists of the emitter and a commercial detector placed 5 mm apart in a simple tube. Operating the emitter at 10 Hz with a power consumption of only 40 mW, the sensor was measured in the range of 6-14% by volume of CO₂, showing a resolution of 0.5%, a response time of 20 s, and low cross-sensitivity to humidity.