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A Preliminary Study of Helmholtz Resonant for Measurement of Watermelon Volume

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131619931,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: @2013
Authors:   Huarui Chen, Huirong Xu, Xiuqin Rao, Naoshi Kondo, Junqi Bao
Keywords:   Helmholtz resonant watermelon volume fast and non-destructive measurement

Abstract. Fruit volume and density are vital features for fruit quality. In a Helmholtz resonant system the resonant frequency was found having a close relationship with the effective volume of the resonator. The objective of this study was to develop a watermelon volume measurement system using the Helmholtz resonant principle. A device consisting of a signal generator, an amplifier, a loudspeaker, a resonator, a microphone, a data acquisition module and a data analysis software was designed and tested. To evaluate the performance of the system, 65 watermelons from native orchard were used. Single-factor tests and orthogonal tests showed that the optimal factor of the watermelon volume measurement system was 6 s of data- acquisition time, 280 mm of distance between microphone to resonator port opening and 100 mm of height between loudspeaker to resonator port opening. The volumes of watermelons were estimated using this system based on the model formula between the resonant frequency and the volume of the resonator chamber with watermelon inside, and the actual volumes of watermelons were measured by water-filling method sequentially. The determination coefficients R2 for the calibration sets (47 watermelons) and validation sets (18 watermelons) were 0.9655 and 0.9568, respectively. It was confirmed that the Helmholtz resonance showed great potential in measuring the volume of watermelon and the following study could reach to density prediction and watermelon internal quality evaluation.

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