A Medium-Range Hygrometer Using Nano-Porous Thin Film of $\gamma $ -$\hbox{Al}_{2} \hbox{O} _{3}$ With Electronics Phase Detection

Present work deals with the development of a low-cost prototype RH meter for measuring humidity in the range of 1-10% RH. The sensor working on capacitive technique consists of porous thin film of γ-AI2O3 formed between the parallel gold electrodes. The film was fabricated by dipcoating of sol solution obtained from the sol-gel method. The pore morphology of the sensor has been characterized by XRD, FESEM and BET analysis. The electrical parameters of the sensor have been determined by Agilent 4294A impedance analyzer. Response (~ 10 s) and recovery (~ 16 s) times of the sensor are better than the commercial sensor utilized for calibration (Xentaur, USA, LPDT-100). A suitable signal condition circuit has been developed to convert the capacitance change into voltage signal. For direct display of the humidity, the output of the sensor has been linearized by diode function generation. The prototype instrument has the potential for measuring humidity in different applications.

[1]  Enrico Traversa,et al.  Ceramic sensors for humidity detection: the state-of-the-art and future developments , 1995 .

[2]  Z. M. Rittersma,et al.  Recent achievements in miniaturised humidity sensors—a review of transduction techniques , 2002 .

[3]  Debdulal Saha,et al.  Sol–gel processed Al2O3 thick film template as sensitive capacitive trace moisture sensor , 2005 .

[4]  Bulent E. Yoldas,et al.  Alumina gels that form porous transparent Al2O3 , 1975 .

[5]  K. G. Ong,et al.  Highly Ordered Nanoporous Alumina Films: Effect of Pore Size and Uniformity on Sensing Performance , 2002 .

[6]  Development of commercial nanoporous trace moisture sensor following sol–gel thin film technique , 2008 .

[7]  S. M. Tebcherani,et al.  Structural characterization of phase transition of Al2O3 nanopowders obtained by polymeric precursor method , 2007 .

[8]  Xiujian Zhao,et al.  Sol–gel fabrication of compact, crack-free alumina film , 2007 .

[9]  Chi-En Lu,et al.  Humidity Sensors: A Review of Materials and Mechanisms , 2005 .

[10]  Noboru Yamazoe,et al.  Humidity sensors: Principles and applications , 1986 .

[11]  Wolfgang Benecke,et al.  A novel surface-micromachined capacitive porous silicon humidity sensor , 2000 .

[12]  T. Islam,et al.  $\gamma-\hbox{Al}_{2}\hbox{O}_{3}$ -Coated Porous Silicon for Trace Moisture Detection , 2011, IEEE Sensors Journal.

[13]  Pasqualina M. Sarro,et al.  Relative humidity sensors using porous SiC membranes and Al electrodes , 2004 .

[14]  G. Blaise,et al.  Physics of Dielectrics , 2013 .

[15]  J. Franca,et al.  A CMOS humidity sensor with on-chip calibration , 2001 .

[16]  Be Yoldas,et al.  A TRANSPARENT POROUS ALUMINA , 1975 .

[17]  E. Teller,et al.  On a Theory of the van der Waals Adsorption of Gases , 1940 .