Sensitivity monitoring of amperometric gas sensors based on impedance spectroscopy

For a large variety of gases, amperometric gas sensors work with high reliability. While the zero point of these sensors is relatively stable in time, the sensitivity and cross-sensitivity can change considerably over time, resulting in incorrect measurements. This can be critical for many applications. Hence, a permanent monitoring of the sensitivity is desired. This paper describes a simple method for automatic monitoring of the sensitivity of amperometric gas sensors, based on impedance spectroscopy measurements. The results show a strong correlation of the sensor sensitivity with the sensor´s double-layer capacity, providing a comfortable tool to monitor the sensors behaviour. An on-line approximation of the characteristic sensor parameters is carried out.