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In this paper, a humidity sensor based on CuO has been successfully fabricated. Thin-film of CuO nanorices were synthesized by Successive Ionic Layer Adsorption and Reaction (SILAR) method on silicon wafer with Si3N4thinlayer as a substrate. The microstructure and morphology of the samples were investigated using X-ray diffraction(XRD) and scanning electron microscopy (SEM). Humidity sensing properties of the thin films have been studied. The sensing response has been measured in the relative humidity (RH) range from 20 up to 80 % at room temperature. It was found that impedance of the system decreases as the RH was increased. The prepared sensor revealed good reversibility with response and recovery time of 130 s and 320 s respectively. The complex impedance spectra were analyzed in the range of 0.1 to 1 kHz. This type of humidity sensor can be used as a new generation of ecological sensors with low cost and good stability. It makes the sensor a candidate for practical applications.

SUMMARY This paper reports on the development of models to estimate the breakdown voltage of air in uniform and non‐uniform gap configurations for the very low frequency (VLF) and low‐frequency (LF) bands. The breakdown voltage of air at VLF/LF is considerably lower and has a larger dependency on ambient humidity than at 60 Hz. Both characteristics have been explained by increased space charge formation at the higher frequencies. The models are shown to be useful for predicting breakdown voltages at VLF/LF for uniform field gap spacings up to 125 mm and non‐uniform field gap spacings up to 4 m. Copyright © 2011 John Wiley & Sons, Ltd.

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