Identification of CO and NO2 using a thermally resistive microsensor and support vector machine

Levels of carbon monoxide and nitrogen dioxide in air are currently monitored using two different thick-film resistive gas sensors. The resultant high power consumption of thick-film-based gas sensors is problematic for portable multi-gas monitors. The use of a single low-power thermally-modulated resistive gas sensor to monitor simultaneously both gases is reported. The silicon micromachined substrate not only reduces the DC power consumption to 100 mW at 300°C but also permits AC temperature modulation through a small thermal mass. Uniquely, a support vector machine is employed to classify the wavelet coefficients of the AC resistive signal. This simple method permits the rapid classification of CO/NO₂ gas mixtures with a high level of confidence (94% or better) using just one low-power gas microsensor. Thus demonstrating the potential application of a single low-power thermally-modulated resistive gas sensor in portable multi-gas monitors.