DETERMINING MOISTURE-CONTENT IN SMALL WHEAT SAMPLES BY DUAL-FREQUENCYRF IMPEDANCE SENSING

A technique is described for estimating moisture content of small samp les of hard red winter wheat (10 to 30 kernels) by impedance measureme nts at I and 4.5 MHz on a parallel-plate capacitor holding the sample between the plates. The measurement system was calibrated by measureme nts on samples, ranging from 9 to 20% moisture content, wet basis, fro m three wheat cultivars grown in 1991 and 1992. Validation measurement s were taken for prediction of moisture content of small wheat samples from three different cultivars harvested in 1992. Moisture contents o f the small samples were predicted with a five-variable equation invol ving differences in the real and imaginary components of the complex i mpedance at the two frequencies. The standard error was 0.9% moisture content. The study established a basis for further development of the rapid, nondestructive method for estimating moisture content of small wheat samples.