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Investigation of the humidity effects on SnO2-based sensors in CO detection

Published online by Cambridge University Press:  01 February 2011

Cesare Malagu'
Affiliation:
malagu@fe.infn.it, university of ferrara, physics, via saragat 1c, ferrara, N/A, 44100, Italy, +390532974294, +390532974325
Michele Benetti
Affiliation:
benetti@fe.infn.it, University of Ferrara, Physics, via Saragat 1/c, Ferrara, N/A, 44100, Italy
Maria Cristina Carotta
Affiliation:
carotta@fe.infn.it, University of Ferrara, Physics, via Saragat 1/c, Ferrara, N/A, 44100, Italy
Alessio Giberti
Affiliation:
giberti@fe.infn.it, University of Ferrara, Physics, via Saragat 1/c, Ferrara, N/A, 44100, Italy
Vincenzo Guidi
Affiliation:
guidi@fe.infn.it, University of Ferrara, Physics, via Saragat 1/c, Ferrara, N/A, 44100, Italy
Luciano Milano
Affiliation:
milano@fe.infn.it, University of Ferrara, Physics, via Saragat 1/c, Ferrara, N/A, 44100, Italy
Giuliano Martinelli
Affiliation:
martinelli@fe.infn.it, University of Ferrara, Physics, via Saragat 1/c, Ferrara, N/A, 44100, Italy
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Abstract

An algorithm for compensating water vapor pressure in CO detection is proposed here and tested on SnO2 thick-film gas sensors. For each sensor working at a fixed temperature, the conductance, G, is fitted by an analytical surface, whose expression can be inverted to determine the CO concentration once the water partial pressure is measured. As soon as the rate of water-vapor pressure change is slower than about 300 Pa/min, G is a function of the temperature, water vapor and CO concentration. If quicker water vapor variations occur instead, the sensing film undergoes a non-negligible transitory phenomenon during which G assumes different values even at fixed water vapor pressure and temperature. This phenomenon prevents the compensation from working properly. An explanation of the behavior is offered by the interpretation of kinetics equations at surface.

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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