Drift phenomenon of capacitive-type relative humidity sensors in a hot andhumid atmosphere

Citation
M. Matsuguchi et al., Drift phenomenon of capacitive-type relative humidity sensors in a hot andhumid atmosphere, J ELCHEM SO, 147(7), 2000, pp. 2796-2799
Citations number
10
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physical Chemistry/Chemical Physics","Material Science & Engineering
Journal title
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
ISSN journal
0013-4651 → ACNP
Volume
147
Issue
7
Year of publication
2000
Pages
2796 - 2799
Database
ISI
SICI code
0013-4651(200007)147:7<2796:DPOCRH>2.0.ZU;2-6
Abstract
The long-term aging effects on capacitive-type relative humidify sensors in a hot and humid atmosphere were investigated to better understand the mech anism of the drift phenomenon. For this purpose, four kinds of polymers, ce llulose acetate (CA), cellulose acetate butyrate (CAB), poly(methyl methacr ylate) (PMMA), and cross-linked polyimide (PI) were used as sensing materia ls. For all sensors, the electrical capacitance increased with aging in a 4 0 degrees C and 90% relative humidity atmosphere. The QCM measurement showe d that the drift of the sensor capacitance was caused by the increase in th e water sorption ability of the sensing polymers. From XPS data, the increa se in the water sorption ability could be attributed to the introduction of the oxygen-containing group at the surface of the sensing polymers. Morpho logical changes were also suggested by the film thickness measurement. Furt hermore, it was confirmed that the magnitude of the drift was affected not only by the increment but also by the state of the sorbed water. Fourier tr ansform infrared data indicated that the sorbed water in the hydrophobic po lymers such as PMMA and PI are close to the isolated state and that the sta te is hardly affected by aging. Because the change in the isolated water do es not significantly affect the electrical capacitance, PMMA and PI sensors show little drift even after 250 days aging. (C) 2000 The Electrochemical Society. S0013-4651(00)01-074-0. All rights reserved.