Abstract
A moisture detection of single rice grains using a slim and small open-ended coaxial probe is presented. The coaxial probe is suitable for the nondestructive measurement of moisture values in the rice grains ranging from from 9.5% to 26%. Empirical polynomial models are developed to predict the gravimetric moisture content of rice based on measured reflection coefficients using a vector network analyzer. The relationship between the reflection coefficient and relative permittivity were also created using a regression method and expressed in a polynomial model, whose model coefficients were obtained by fitting the data from Finite Element-based simulation. Besides, the designed single rice grain sample holder and experimental set-up were shown. The measurement of single rice grains in this study is more precise compared to the measurement in conventional bulk rice grains, as the random air gap present in the bulk rice grains is excluded.
Highlights
There has been an increased interest in microwave measurement techniques for the determination of moisture content, m.c. of bulk rice grains in the microwave frequencies range [1,2,3,4,5]
The m.c. for a bulk rice grain sample is a statistical mean value due to the slightly different m.csingle of each single grain
This will lead to a scattered measurement of the reflection coefficient, ΓBB’, of the single grain in referring to the average m.c. of the bulk sample, as shown in Figure 6 does show a significant change of the measured reflection coefficient, ΓBB’ of a single rice grain with the m.c. of bulk rice grain
Summary
There has been an increased interest in microwave measurement techniques for the determination of moisture content, m.c. (or dielectric properties) of bulk rice grains in the microwave frequencies range [1,2,3,4,5]. There has been an increased interest in microwave measurement techniques for the determination of moisture content, m.c. Chemical reaction methods (extracting water using the reaction of iodine in sulfur dioxide) Both methods remove the moisture determine the true water content by the resulting weight loss. The prime considerations in the measurement of grain moisture using indirect methods are the size of the instrument sensor, which is in direct contact with the rice grain samples and the accuracy of the measurements [5]. The measurement using commercial open-ended waveguides is suitable for a specific rice grains size (width and length). A millimeter size slim open-ended coaxial probe has been fabricated to measure the moisture in small grains.
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