Rice Grain Moisture Determination Using Microstrip Wide-Ring and Microstrip Coupled-Line Sensors

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.

Microstrip Moisture Sensor Based on Microstrip Patch Antenna

“…The MC range varies from 10.71% to 21.87% at operated dual frequencies, The MRE was 0.55% between PMC and AMC, which clearly shows that this MRE is much lower than existing sensors' MRE (Ref. [26]). The experiment measurements show that the reflection coefficients increase with the increment of MC of samples.…”

“…Ref. [26] proposed a microstrip ring sensor at dual frequencies (4.36 MHz and 10.69 MHz) with outer radius 17.96 mm and inner radius 8.92 mm. The sensor was fabricated on RT-Duroid 5880 (expensive).…”

“…Ref. [26] designed the sensor at operated frequency 4.36 GHz and 10.69 GHz, fabricated on RT Duroid 5880 (expensive) with the outer radius and inner radius (R o × R I = 17.96 mm × 8.92 mm). The regression coefficient was obtained as 0.9705 and 0.9383 at frequency (4.36 GHz and 10.69 GHz).…”

“…To measure moisture in hevea rubber latex, a U-shaped antenna has been described [18]. A moisture sensor has been rendered based on the microstrip antenna which is operated on dual frequencies [19][20][21][22][23][24][25][26].…”

Physical and Chemical Characterization of Rice Using Microwave and Laboratory Methods

“…The coupling effects between the two slots will increase the density of the sensing fields for the sensor. Recently, microstrip wide-ring, microstrip coupled-line [9] and small coaxial probe [10], as shown in Figure 9, have been used for rice moisture measurements. By using wide-ring and coupled-line sensors, the bulk rice grain samples with different levels of m.c.…”