Gas selectivity of low-concentration oxidizing-gas sensor using complex impedance method

In recent years, because of increased fuel consumption and carbon dioxide emissions problem, the diesel engine has been attracting attention. However, diesel engines produce more nitrogen oxide and sulfur oxide than gasoline engines. The effects on the human body exceed regulation guidelines. Therefore, these gases should be detected and measured. In this paper, we studied the measurement of mixture gases using the complex impedance of a low-concentration oxidizing gas sensor. We determined that it is possible to measure mixed gases in the range of 0.1–0.9 ppm for nitrogen dioxide and 0.6–1.4 ppm for sulfur dioxide owing to the difference in the complex-impedance change pattern.