He. Endres et al., A THIN-FILM SNO2 SENSOR SYSTEM FOR SIMULTANEOUS DETECTION OF CO AND NO2 WITH NEURAL SIGNAL EVALUATION, Sensors and actuators. B, Chemical, 36(1-3), 1996, pp. 353-357
Simultaneous CO and NO2 measurements are of importance for the ventila
tion control of automobiles and other applications, For this purpose s
emiconducting SnO2 sensors are often used. A well known disadvantage o
f SnO2 sensors is the concurrent reaction of the oxidizing NO2 and the
reducing CO on the sensor surface, which causes a near zero sensor si
gnal in the presence of both gases in a certain range of mixtures. A s
econd disadvantage of SnO2 sensors are the long rise and decay times o
f the sensor signal. The combination of different SnO2 sensors, operat
ed at different temperatures and combined with a signal evaluation sys
tem based on a specially trained neural forward network (artificial ne
ural net (ANN)) solves this problem. The runtime version of the neural
net is a small program, compatible with customary micro controllers.
These signal evaluation techniques are applicable to similar problems
using sensor arrays or single sensors in a non-stationary operating mo
de.