Analysis of CO and CH4 gas mixtures by using a micromachined sensor array

An array of highly sensitive and mechanically stable gas sensors based on different sol–gel fabricated Pd-doped SnO2 nanocrystalline thick films has been developed for the analysis of ternary mixtures in the concentration ranges of 0–100 ppm CO, 0–4000 ppm CH4 and 0–50% relative humidity. The selectivity of the sensors has been modulated by varying the percentage of Pd content and the contacts geometry, while the use of micromachined hotplates as substrates for the sensors allowed a reduction of heater power consumption and a fast and accurate temperature control. Principal component analysis (PCA) as pattern recognition and principal component regression (PCR) as multicomponent analysis method have been used to analyze these mixtures qualitatively and quantitatively obtaining good results.