Development of replaceable sensing element tester for optical-based humidity sensor

Saari, Nurul Syarmila (2024) Development of replaceable sensing element tester for optical-based humidity sensor. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

The project is about the development of a sensing element tester on optical -based humidity sensor device. There were many research studies on the optimization of ZnO nanorods growth condition such as ZnO growth durations, ZnO nanorods coating area or growth process parameters towards optimum sensing response for humidity detection. However, researchers faced inconsistency issues when they had to re-setup the device for testing every sample they tested which cause variations in the measurements and difficult to conclude the optimized parameter for the best sensing response. Therefore, a sensing device with the capability of a replaceable sensing material was needed to ensure the consistency of the sensing setup. This project utilized a glass substrate as the light medium, with a commercial Light-Emitting Diode (LED) as the light source and a photodiode as the photodetector placed at both ends of the glass so that the light travels from the LED towards the photodiode through the glass substrate. ZnO nanorods were fabricated on the surface of several thin microscope cover glasses with variations in growth duration. This enables the ZnO-coated thin cover glass easily replaced on the glass substrate without affecting the sensor setup. The fabricated samples were then characterized against humidity sensing and analyzed the impact of growth durations. It was found that the sample with 9 h of growth time exhibited higher output voltage reading as compared to 3 h sample during initial characterization without humidity sensing. In humidity sensing, it was observed that the 9 h sample produced higher sensing response towards humidity detection with the sensitivity of -6.77 mV/%. This project helps researchers streamline the optimization process of sensing performance and enhanced the consistency of measurement.

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