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Design and Development of Thin film Humidity Sensor based on Alumina and Zirconium dioxide
Published in Institute of Electrical and Electronics Engineers Inc.
Measurement of humidity is one of the most significant issues in various areas of applications such as an agriculture, automated system, instrumentation, climatology and GPS. In this paper, a cost effective thin film impedance type humidity sensor is proposed to detect the moisture content in the ambient environment. The ceramic material alumina is used as a substrate over which a thin film of zirconium dioxide is deposited by RF (Radio frequency) Sputtering at 13.5 MHz. An interdigitated pattern of aluminium electrode is coated over the active sensing layer by thermal evaporation technique. The parallel plates of electrode with active sensing material (ZrO2) as dielectric constitute the capacitive structure. When the sensor is exposed to the ambient air containing moisture, the impedance of the sensing material varies. As the electrical permittivity of the ambient air is a function of relative percent humidity, this sensor is used for measuring the relative humidity in the ambient air. To test the performance of this device, an acrylic chamber is developed to assure that the measurements are free from external effects. An artificial moisture environment is created by placing a humidifier inside the chamber along with the fabricated sensor. The output of the sensor is interfaced with labview data acquisition which continuously monitored the humidity level sensed by the sensor. The relative humidity sensitivity of the device at an operating frequency range of 100 kHz to 1 MHz is 2.226.The humidity hysteresis error of 2.01 % is observed from the device. The designed humidity sensor shows a fast sensing response and the results obtained are validated by comparing with the test results of DHT11. © 2020 IEEE.