Instrument For Single-kernel Nondestructive Moisture Measurement

A prototype instrument, constructed for practical demonstration of the nondestructive measurement of moisture content in single corn kernels by RF impedance measurements at frequencies of 1.0 and 4.5 MHz, is described. The principles of the measurement are presented. The mechanical single-kernel feeder and parallel-plate electrode assembly that form a part of the instrument are described. The impedance magnitude and phase measuring electronic circuits designed and constructed for the instrument are also described briefly. In initial calibration and performance tests with corn ranging from 11 to 25% moisture, wet basis, more than 80% of the kernels were measured to within 1% moisture content of reference values determined by oven-drying procedures.