The capacitive humidity sensor is normally fabricated by an interdigitated electrode (IDE) or parallel plate structure. In this paper, 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 ( $\gamma $ -Al2O3) was deposited on the inner wall of the quartz tube for adsorbing humidity. The four symmetrical silver electrodes of the cross-capacitor are formed around the quartz tube by the screen printing technique. The sensor has been tested for different levels 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%), and 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 considerably improved.

中文翻译：

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基于薄膜多孔氧化铝的交叉电容湿度传感器

电容式湿度传感器通常由叉指电极 (IDE) 或平行板结构制成。在本文中，首次利用 Thompson-Lampard 定理提出的交叉电容原理来制造精密和准确的相对湿度 (%RH) 传感器。在石英管的内壁上沉积一层多孔氧化铝薄膜（$\gamma$ -Al2O3）用于吸附湿气。交叉电容器的四个对称银电极通过丝网印刷技术围绕石英管形成。该传感器已针对 0–90 % RH 范围内的不同湿度水平进行了测试。制造的传感器的电容响应非常准确 (±2%RH)、高度可重复 (±0.01%)、极低的滞后 (±0.3%) 和较小的漂移。因此，它可用于制造商业应用的湿度计。交叉电容器的主要优点是一维精度。发现没有任何亲水膜的湿度传感器的灵敏度较低。然而，通过在石英管的内表面沉积薄传感膜，灵敏度得到了显着提高。