Parallel-plate impedance sensing of moisture content in single seeds and grain kernels

The moisture content of single field corn, popcorn and peanut kernels, soybean seeds, single in-shell pecan nuts and pecan kernel halves were sensed by measuring the impedance of a small parallel-plate capacitor with the kernel, seed, or nut between and in contact with the plates at two frequencies between 1 and 5 MHz. Standard deviations of differences between moisture contents determined by the impedance measurements and those determined by over-drying reference methods ranged from 0.5 to 0.7% moisture. These levels are sufficiently accurate for most practical purposes. This performance was achieved on all lots tested with randomly selected kernels. Satisfactory results were obtained independently of shape and size variation among the kernels.<>