CO2 Sensor using Quartz Crystal Microbalance Coated with Sensitive Membrane

概要

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We tried to make a CO2 sensor using a quartz crystal microbalance (QCM) coated with acrylonitrile-styrene copolymer (AS). Concentration of CO2 gas diluted with dry N2 gas was measured using the QCM whose output is frequency shift. Sensitivity of the QCM to Ar, O2 and humidity was also examined because atmosphere is composed of N2, O2, CO2, Ar and water vapor. Consequently it was revealed that the QCM coated with AS is sensitive to not only CO2 but humidity and insensitive to O2 and Ar. Next relationships between concentration of CO2 gas diluted with damp N2 gas and frequency shift of the QCM were examined. Consequently it was clarified that the frequency shift compensated for influence of humidity is nearly equal to the frequency shift caused by CO2 gas diluted with dry N2 gas. Accordingly it was shown that concentration of CO2 gas in atmosphere can be measured using the QCM. Furthermore it was found that sensitivity to concentration of CO2 and humidity grows higher with increasing thickness of AS membrane.