MICROWAVE SENSING OF MOISTURE CONTENT AND BULK DENSITY IN FLOWING GRAIN AND SEED

Current techniques for rapid moisture measurement of grain and seed through sensing the dielectric properties in the 1 to 200 MHz frequency range require correction for density fluctuations and therefore are not suitable for reliable measurements on flowing grain. Density-independent moisture sensing in grain and seed is possible at microwave frequencies and has been successfully demonstrated on static samples. Bulk density of flowing grain can also be sensed simultaneously with moisture content. Although the theoretical basis for density-independent grain moisture measurement is expected to be useful for flowing materials, successful use has not previously been demonstrated. A laboratory flowing grain system was built for tests of microwave moisture measurement that were conducted on shelled field corn, wheat, and soybeans. Appropriate software was written to control a microwave network analyzer for the necessary attenuation and phase measurements, and tests were run on flowing grain and seed materials at high and low moisture levels and at low, medium, and high flow rates. Results confirmed that moisture readings obtained on static and flowing grain and seed agreed well, demonstrating the usefulness of the microwave density-independent technique for monitoring moisture content of flowing grain and seed. Bulk density determinations of static and flowing grain and seed also agreed well, indicating the usefulness of the technique for monitoring bulk density when desired.