RF IMPEDANCE SENSING OF MOISTURE-CONTENT IN INDIVIDUAL DATES

Measurements of the impedance at 1 and 5 MHz of a parallel-plate elect rode assembly with individual dates between the electrodes predicted d ate flesh moisture content with a standard error of about 1% moisture content (m.c.) over the range from 13 to 22%. The predictions on Calif ornia Deglet Noor dates from the 1990 crop were based on a calibration equation developed previously on dates from the 1988 and 1989 crops. Combining data on dates of 12% m.c. or higher from all three crop year s provided a new calibration, which permits computation of m.c. from m easurements of capacitance only at the two frequencies. The instantane ous, nondestructive m.c. sensing technique is recommended for further development for on-line sorting to reduce the skilled-labor requiremen ts in the sorting and grading of fresh dates.