Humidity sensors: A review

Abstract

Humidity is one of the most commonly measured physical quantities and is of great importance in a wide variety. This paper reviews the transduction techniques of various state-of-the-art humidity sensors, including (1) optical, (2) gravimetric, (3) capacitive, (4) resistive, (5) piezoresistive, and (6) magnetoelastic sensors. Starting from the fundamental operation principles, critical issues about design, fabrication, characterization and applications of these humidity sensors were reviewed. It is notable that promising technologies has been applied to revolutionize the design of the humidity sensors. Smaller, faster, cheaper humidity sensors have been reported in the published literatures. However, it still remains challenging to develop a humidity sensor which provides a complete set of favorable characteristics, e.g., good linearity, high sensitivity, low hysteresis and rapid response time. Copyright © 2005 American Scientific Publishers. All rights reserved.