Abstract
Determining the Moisture Content (MC) inside rice grain is an important element for grain processesing such as harvesting, storage, quality control and transportation. A microstrip wide-ring sensor and a microstrip coupled-line sensor with low insertion loss were developed to operate at relatively low frequency to determine the MC and relative complex permittivity of rice grain. The complex permittivity for rice grain with various moisture levels was measured by the proposed sensors based on the resonance technique. Calibration equations for measurement of grain MC were obtained and validated with white rice for MC ranging from 10 to 28% wet basis. The coupled-line sensor showed better sensitivity to moisture measurement as compared to the wide-ring sensor. For a 1% change in MC, the changes of resonant frequency for the wide-ring and coupled-line sensors were 4.36 and 10.69 MHz respectively. Meanwhile, the wide-ring sensor had a higher accuracy in MC prediction than the coupled-line sensor. The average errors in moisture prediction for wide-ring and coupled-line sensors were 0.85 and 1.30% respectively.
Highlights
Rice is a main source of nutrition for human beings especially for Asiatic populations
This paper proposes microstrip wide-ring and microstrip coupled-line sensors for rice grain Moisture Content (MC) and relative complex permittivity measurements
A microstrip wide-ring and a microstrip coupled-line sensor with low insertion loss have been presented as non-destructive sensors for rice grain MC and relative complex permittivity measurement
Summary
Rice is a main source of nutrition for human beings especially for Asiatic populations. Moisture Content (MC) inside rice grain is a crucial parameter for grain processing such as harvesting, storage, quality control and transportation. Rice grain is usually harvested between 19 and 25% MC for maximum grain yield and needs to be dried to 14% or less, depending on the season and the weather, for safe storage. Precise determination of the rice grain MC is important. The conventional standard method for MC determination for grain is the oven-drying method. This can achieve high precision, it is timeconsuming and impractical. Microwave technique was applied in MC determination for oil palm fruit (You et al, 2010a), soybean (Shrestha et al, 2014), tuber (Zainuddin et al, 2013), clay granule (Mextorf et al, 2012), latex (Ansarudin et al, 2012; Mohammadi et al, 2012) and mortar (Jusoh et al, 2011)
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