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Abstract
Present work deals with the development of a capacitive humidity sensor using porous thin film of aluminium oxide on the interdigitated gold electrodes. We describe the effect of polyethylene glycol (PEG) addition to pure sol solution of γ-Al2O3 on the humidity sensing characteristics of the sensor. The film was fabricated by dip coating of sol solution obtained from the sol-gel method. To compare the response characteristics, three different sensors such as pure alumina sol, 0.125 g and 1 g PEG added in pure sol have been fabricated. The electrical parameters of the sensor have been determined by Agilent 4294A impedance analyzer. The sensor so obtained was found to be sensitive in humidity range of 1 to 90%. Addition of fixed amount of PEG in pure alumina sol improved the response characteristics significantly. The response time of the 0.125 g PEG added sensor was very low, about 10 s and the recovery time was about 3 s. The behaviour of the most sensitive sensor has been modelled with a view to minimize the error and was fitted well with the experimental data.