Journal of Biosystems Engineering

Korean Society for Agricultural Machinery (한국농업기계학회)
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Study on Non-contact Ultrasonic Transducer for Measurement of Fruit Firmness

과실 경도측정을 위한 비접촉 초음파 변환기 연구

  • Lee, Sang-Dae (Agricultural Research Service, USDA) ;
  • Ha, Tae-Hoon (Dept. of Medical Physics, University of Science & Technology) ;
  • Kim, Ki-Bok (Center for Safety Measurement, Korea Research Institute of Standards and Science) ;
  • Kim, Man-Soo (Dept. Biosystems Machinery Engineering, Chungnam National University)
  • Received : 2010.04.12
  • Accepted : 2010.05.28
  • Published : 2010.06.25
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Abstract

This study was conducted to develop an non-contact ultrasonic transducer for measurement of fruit firmness. The center frequency of non-contact ultrasonic transducer was 500 kHz. As an active element of non-contact ultrasonic transducer, the 1-3 piezoelectric composite material was selected. That material has high piezoelectric properties such as electro-mechanical coupling factor, $k_t$ and piezoelectric voltage constant, $d_{33}$ and also that material has low acoustical impedance which enables to matching the acoustical impedances between piezoelectric material and air. As a front matching material between 1-3 piezoelectric composite material and air, various kinds of paper with different thickness were tested. To control the dead-zone of the fabricated non-contact ultrasonic transducer, the backing material composed of epoxy resin and tungsten powder were made and evaluated. The fabricated non-contact ultrasonic transducer for fruit showed that the cneter frequency, bandwidth and beamwidth were approximately 480 kHz, 30 % and 12 mm, respectively. It was concluded that non-contact measurement of apple firmness would be possible by using the fabricated non-contact ultrasonic transducer.

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References

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  1. Predicting the Firmness of Apples using a Non-contact Ultrasonic Technique vol.38, pp.3, 2013, https://doi.org/10.5307/JBE.2013.38.3.192