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Nondestructive Measurement of Moisture Content of Different Varieties of Wheat Using a Single Calibration with a Parallel-Plate Capacitance Sensor

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASABE. 55(4): 1583-1587. (doi: 10.13031/2013.42227) @2012
Authors:   C. V. K. Kandala, J. Sundaram, N. Puppala, V. Settaluri
Keywords:   Capacitance, Impedance analyzer, Moisture content, Parallel-plate electrodes, Phase angle, Wheat

A simple, low-cost instrument that measures impedance and phase angle was used along with a parallel-plate capacitance system to estimate the moisture content (MC) of six varieties of wheat. Moisture content of grain is important and is measured at various stages of processing and storage. A sample of about 150 g of wheat was placed separately between a set of parallel plate electrodes, and the impedance and phase angle of the system were measured at frequencies 1 and 5 MHz. A semi-empirical equation was developed using the measured impedance and phase angle values, the computed capacitance, and the MC values obtained by standard air-oven method. Multiple linear regression (MLR) was used for the empirical equation development using statistical software. In the present work, a low-cost impedance analyzer, designed and assembled in our laboratory, was used to measure the impedance and phase angles. MC values of wheat samples in the moisture range of 9% to 25%, not used in the calibration, were predicted by the equations and compared with their standard air-oven values. For over 97% of the samples tested from the six varieties of wheat, the predicted MC values were within 1% of the air-oven values. This method, being nondestructive and rapid, will have considerable application in the drying and storage processes of wheat and similar field crops.

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