Analysis of Frequency Sensitivity of the Unified Grain Moisture Algorithm

Abstract

The purposes of this research were: 1) to reconfirm the use of 149 MHz as the appropriatemeasurement frequency for the Unified Grain Moisture Algorithm, 2) to assess what moisturemeasurement errors might result from a manufacturer choosing a frequency other than 149 MHz,and 3) to estimate the frequency accuracy and stability needed for moisture meters to be compatiblewith the Unified Grain Moisture Algorithm. Dielectric data for over 6,000 grain samples were used tosimulate the effects of different measurement frequencies. Programs were written to re-optimize allparameters so that the relative performance at different measurement frequencies could bethoroughly evaluated. The results reconfirmed the original choice of approximately 149 MHz as adesirable measurement frequency. With limited re-optimization efforts, other measurementfrequencies within several megahertz of 149 MHz could be used with little or no performancepenalty. Measurement frequency error (ambiguity) caused much larger moisture measurement errorsthan intentional changes with appropriate parameter adjustments. The frequency accuracy andstability for instruments based on the Unified Grain Moisture Algorithm should be better than +/- 0.1MHz to have negligible effects on moisture measurement accuracy.