A Thin Film Porous Alumina-Based Cross-Capacitive Humidity Sensor (original) (raw)

2019, IEEE Transactions on Instrumentation and Measurement

The capacitive humidity sensor is normally fabricated by interdigitated electrode (IDE) or parallel plate structure. In this work, the principle of the cross-capacitance proposed by Thompson-Lampard theorem has been utilized for the first time to fabricate a precise and accurate relative humidity (%RH) sensor. A thin film of porous alumina (γ-Al 2 O 3) was deposited on the inner wall of the quartz tube for adsorbing humidity. The four symmetrical silver electrodes of the crosscapacitor are formed around the quartz tube by screen printing technique. The sensor has been tested for different level of humidity in the range of (0-90 %RH). The capacitive response of the fabricated sensor was very accurate (± 2 %RH), highly repeatable (± 0.01%), very low hysteresis (± 0.3%), less drift. Thus, it can be used for making hygrometer for commercial applications. The main advantage of the cross-capacitor is the single dimensional accuracy. The sensitivity of the sensor for humidity without any hydrophilic film was found to be less. However, by depositing the thin sensing film on the inner surface of the quartz tube, the sensitivity was improved considerably.

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