Calibration of a microwave system for measuring grain moisture content

This paper relates to a microwave system for grain moisture content determi nation which is based on simultaneous measurements of two parameters: atten uation and phase shift, of the electromagnetic wave transmitted through the layer of material. The calibration of such a system consists of identifyin g a function modeling the relationship between these parameters and the mea sured moisture content, Laking into account an influence quantity-temperatu re T. Two algorithms for calibration are proposed and studied. The results of calibration show that the moisture of hard red winter wheat can be deter mined with uncertainty less than 0.5% moisture, at the 95% confidence level , in the moisture range of 10% to 19% at grain temperatures between -1 degr ees C and 42 degrees C, independent of the grain bulk density.