Resistive Humidity Sensors

Authored by: Ghenadii Korotcenkov

Handbook of Humidity Measurement

Print publication date:  February  2019
Online publication date:  January  2019

Print ISBN: 9781138300224
eBook ISBN: 9780203731888
Adobe ISBN:

10.1201/b22370-11

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Abstract

In resistive sensors, the humidity measure is a change in the resistance/conductivity of humidity-sensitive film caused by interaction with water vapor. Modulation of electrical conductivity (or electrical conductance) by the presence of water vapor takes place via reactions such as adsorption, chemical reactions, diffusion, and swelling, taking place on the surface or in the bulk of the sensing layer. This modulation can be measured as a change in the current, which is correlated to the concentration of water vapor in the surrounding atmosphere. The structure of conductometric sensors is very simple. These sensors are suitable for mass production and can be characterized by small size and low cost. This chapter gives a detailed description of such sensors. The main attention is paid to polymers and metal oxides. In particular, sensors based on conductive polymers, polymers containing inorganic salts, polyelectrolytes, and nanocomposites are analyzed. Metal oxide–based resistive humidity sensors, including mechanisms of conductivity in metal oxides in humid air and the role of structural factor and alkaline ions in the sensor performance, are also considered in detail. Advantages and disadvantages of resistive humidity sensors, as well as the parameters of sensors manufactured using different approaches, are also analyzed in this chapter.

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