Effect of various flow rate on current fluctuations of amperometric gas sensors

The flow rate of analyte is a key parameter in the measurement system that influences response of gas sensors.
The paper focuses on possibility of improved gas detection by modulation of analyte flow rate around amperometric sensors at equilibrium conditions by studying the direct current level and its fluctuations at selected concentration. To independently explore an impact of concentration and flow rate on spectral density of current fluctuations, all measurements were provided out under the same temperature, and each sample sensor was put to the same position at the test chamber to be under same fluidic condition. The experiments were carried out on the fully-printed amperometric NO2 sensor based on a semi-planar three electrode topology. The aims of this experimental study are two-fold: firstly, to show that spectral density of current fluctuations significantly changes in the level and the shape as flow rate increases at constant concentration of detected gas; and secondly, to demonstrate that evaluation of these fluctuations and DC component can be used to compensate the negative effect of flow rate on sensor responses. The spectral density of current fluctuations develops as several mechanisms related to fluctuation phenomena become dominant with increasing flow rate. Thus, signal-to-noise ratio of current response on detected gas decreases as flow rate increases, while the ratio is almost invariant to gas concentration.