Improvement of measurement accuracy using state equivalence correction for CH4 and CO2 sensor in geochemical application

•Several studies have been conducted to overcome challenges in GGE. Compared with state-of-the-art.•A methods, contributions of this study are presented as follows:•A state equivalence correction (SEC) method based on state observer theory is explored to monitor sensor states and correct measurement errors.•A method for measuring gas pressure deviation using absorption equivalence is proposed for the first time.•A state monitoring method is investigated to analyze the reliability of sensor output.•A prototype of the CH4 and CO2 sensor demonstrates application potential in GGE.