Abstract
The humidity sensing characteristics of different sensing materials are important properties in order to monitor different products or events in a wide range of industrial sectors, research and development laboratories as well as daily life. The primary aim of this study is to compare the sensing characteristics, including impedance or resistance, capacitance, hysteresis, recovery and response times, and stability with respect to relative humidity, frequency, and temperature, of different materials. Various materials, including ceramics, semiconductors, and polymers, used for sensing relative humidity have been reviewed. Correlations of the different electrical characteristics of different doped sensor materials as the most unique feature of a material have been noted. The electrical properties of different sensor materials are found to change significantly with the morphological changes, doping concentration of different materials and film thickness of the substrate. Various applications and scopes are pointed out in the review article. We extensively reviewed almost all main kinds of relative humidity sensors and how their electrical characteristics vary with different doping concentrations, film thickness and basic sensing materials. Based on statistical tests, the zinc oxide-based sensing material is best for humidity sensor design since it shows extremely low hysteresis loss, minimum response and recovery times and excellent stability.
Highlights
Humidity, which is amount of water vapor present in air or atmosphere, is highly variable and changes according to seasons, land, sea, temperature and so on, and has an important role in the quality of industrial products, advanced instruments and human life
Humidity sensors for measuring relative humidity based on different types of materials, including carbon, vanadium, iron, silicon, polymer, tin, titanium, zinc, zirconia, and sodium have been reviewed extensively
The electrical properties of humidity sensors such as resistance and capacitance, the effects of temperature, frequency, and relative humidity, sensitivity, response time, hysteresis and stability have been compared in detail for various materials
Summary
Humidity, which is amount of water vapor present in air or atmosphere, is highly variable and changes according to seasons, land, sea, temperature and so on, and has an important role in the quality of industrial products, advanced instruments and human life. The regulation of humidity is important for human comfort, storage of various goods, industrial process control, high-tech instruments, and plenty of advanced sectors [1]. Optimum humidity conditions should be provided on production lines for obtaining high quality products. In textile processing, generation of electrostatic charges during the fabrication may cause the materials to cling. This is prevented by keeping the environment in damp conditions. The measurement and control of humidity have significant importance in many areas for different purposes
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