Determining the total amount of NOx in a gas stream – Advances in the accumulating gas sensor principle

The accumulating gas sensor principle is a promising concept for selectively measuring low amounts of an analyte by detecting the total amount of the analyte passing the sensor over a given time interval rather than detecting the concentration at any moment. Hereby, the change of the electrical properties of an analyte storage material due to accumulation of analyte molecules serves as the sensor signal. In earlier approaches of an integrating NOx sensor, the sensor signal correlated only with the time integral of the NOx concentration and was independent on the gas flow rate. To overcome the drawback that the flow rate also contributes to the total amount of the analyte gas passing the sensor, we present a novel sensor setup for which all incoming analyte molecules can be stored. The signal of this sensor is proportional to the integration over time of the product of the analyte concentration and the gas flow, resulting in the correct determination of the total amount of NOx.