Performance of Thin Film Humidity Sensors
Abstract
Various hygroscopic materials have been considered for use as the thin film dielectric in a condenser, which is to be used as the humidity sensing element in an electric hygrometer. The requirement of such a dielectric is that it approach equilibrium rapidly and display both reversible and reproducible humidity-electrical characteristics. Polymerous dielectrics have shown an extremely slow rate of response and it is suspected that the rate of Knudsen diffusion through many fine tortuous pores is responsible. Anodic aluminum oxide films produced in a sulfuric acid electrolyte have recently shown a rapid rate of response as well as a reproducible response toward humidity changes. The major limitation hindering the use of such humidity sensing elements is their long-term calibration drift, which causes the elements to become less sensitive toward humidity variations. Results have shown that a change in the concentration of various species of chemisorbed water vapor initially present on the pore walls may be responsible for the observed calibration drift and that further experimentation in this area is warranted.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 15, 1967
- Accession Number
- AD0663757
Entities
People
- Joseph Delpico
Organizations
- Massachusetts Institute of Technology