Characterization of Heterostructure Capacitive Humidity Sensor Using Indirect Capacitance to Voltage Converter Circuit

Fruits can easily become soggy and rot when exposed to a humid environment. Therefore, fruit needs to be placed at a suitable humidity level and maintained at that level from time to time to prevent fruit damage. This paper designs a capacitive humidity sensor with a 281-sensitivity value of a heterostructure composed of hematite and nickel oxide as sensing materials connected to an indirect capacitance to voltage converter circuit, which is a combination of an astable multivibrator circuit and a Zener-regulated frequency to capacitance converter used as a detector circuit with 2.41 mV/%RH sensitivity to determine the humidity level (%). Variations in capacitance values cause variations in the output voltage that can be justified by the amount of water vapor present in fruit packaging. The sensing method is based on the fundamental principle of capacitance changes, which are produced by the interaction of water vapor with sensing material.