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Open AccessArticle

A Novel, Portable and Fast Moisture Content Measuring Method for Grains Based on an Ultra-Wideband (UWB) Radar Module and the Mode Matching Method

1
Department of Automation, Beijing University of Posts and Telecommunications, Beijing 100876, China
2
Department of Biological and Agricultural Engineering, Jilin University, Changchun 130012, China
3
Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
*
Authors to whom correspondence should be addressed.
Sensors 2019, 19(19), 4224; https://doi.org/10.3390/s19194224
Received: 22 August 2019 / Revised: 27 September 2019 / Accepted: 27 September 2019 / Published: 28 September 2019
(This article belongs to the Special Issue Advanced Sensors in Agriculture)
To perform fast and portable grain moisture measurements under field conditions, a novel moisture sensor was designed, which consisted of a coaxial waveguide, a circular waveguide, and an isolation layer. The electromagnetic characteristics of the sensor were simulated and measured. The analytical model, which represented the relationship between the reflection coefficient of the sensor and the complex permittivity of grain, was established by using the mode matching method. The reflection coefficient of the sensor was measured by using an ultra-wideband (UWB) radar module, and the moisture content of grains was calculated from the complex permittivity by using density-independent model. To verify the performance of the proposed method, wheat, rough rice, and barley were taken as examples. The measured results in the range from 1.0% to 26.0%, wet basis, agreed well with the reference values (R2 was more than 0.99), and the maximum absolute errors for wheat, rough rice, and barley were 1.1%, 1.0%, and 1.4%, respectively. In addition, the effect of isolation layer was discussed. Both the simulation results and the experimental results showed that the isolation layer improved the stability of sensor. View Full-Text
Keywords: moisture measurement; grain; ultra-wideband radar; sensors; mode matching method moisture measurement; grain; ultra-wideband radar; sensors; mode matching method
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MDPI and ACS Style

Zhang, C.; Shi, Z.; Yang, H.; Zhou, X.; Wu, Z.; Jayas, D.S. A Novel, Portable and Fast Moisture Content Measuring Method for Grains Based on an Ultra-Wideband (UWB) Radar Module and the Mode Matching Method. Sensors 2019, 19, 4224.

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