Nondestructive Measurement of Moisture Content of Different Types of Wheat with a Parallel-Plate Capacitance Sensor

Abstract

A simple, low cost instrument called the CI meter, that measures impedance and phase angle was used along with a parallel-plate capacitance system to estimate the moisture content (MC) of six types of wheat. MC measurement of grain is important at various stages of their purchase, processing and storage. Samples of about 150 g of wheat at different MC levels were placed separately between a set of parallel plate electrodes, and the impedance and phase angle of the system were measured at 1 and 5 MHz. The MC values of all these samples were obtained by the standard air-oven method A semi- empirical equation was developed using the measured impedance and phase angle values and the computed capacitance, and the oven MC values obtained. Multi Linear Regression (MLR) method was used for the development of the empirical equation. In the present work, a low-cost impedance analyzer designed by Kandala, and assembled in the National Peanut 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 equation develop, and compared with the 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 buying, processing, drying and storage processes of wheat and similar field crops.