Abstract
A new type of capacitive humidity sensor is introduced in this paper. The sensor consists of two plate electrodes coated with MWCNT films and four pieces of isolating medium at the four corners of the sensor. According to capillary condensation, the capacitance signal of the sensor is sensitive to relative humidity (RH), which could be transformed to voltage signal by a capacitance to voltage converter circuit. The sensor is tested using different saturated saline solutions at the ambient temperature of 25 °C, which yielded approximately 11% to 97% RH, respectively. The function of the MWCNT films, the effect of electrode distance, the temperature character and the repeatability of the sensor are discussed in this paper.
Highlights
Humidity sensors, as a kind of humidity measurement devices, are very important in environmental fields, such as medical applications for human comfort, industrial uses, agriculture, automobiles, etc. [1,2].Recently, research on humidity sensing materials has focused on macromolecule compounds [3], semiconductor materials [4], porous silicon [5,6], carbon nitride films [7,8] and porous ceramics [911], etc
Yeow produced a capacitive humidity sensor using carbon nanotubes (CNTs) and the capacity increased while the relative humidity (RH) rose [23]
Varghese et al developed a new type of multiwall carbon nanotubes (MWCNTs) sensor for resistance detection in which the value of the resistance and the RH changed in the same way [24]
Summary
Wei-Ping Chen 1,2, Zhen-Gang Zhao 1,*, Xiao-Wei Liu 1,2, Zhong-Xin Zhang 1 and Chun-Guang Suo 1. Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Ministry of Education, China. Received: 29 June 2009; in revised form: 11 August 2009 / Accepted: 24 August 2009 /
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