Figure 4From: Fast responsive, optical trace level ammonia sensor for environmental monitoringDLR calibration and longtime stability of sensor E. (a) Calibration of sensor E based on phaseshift measurements (red graph mean value of 2 sensor foils) and calculated correlating cotangent values (blue graph); (b) longtime stability comparing illuminated sensors (red graph, mean value of 4 sensor foils) and non-illuminated sensors (blue graph, mean value of 6 sensor foils).Back to article page