Free space traveling–standing wave attenuation method for microwave sensing of grain moisture content

Abstract

Moisture content is an important index to assess the grain quality and food processing conditions. A measurement system based on the traveling–standing microwave attenuation method is designed for a fast and nondestructive grain moisture content determination. The proposed system consists of a microwave cavity oscillator, microwave transmitting and receiving horn antennas, microwave detector, slide rail, sample container, weight sensor, temperature sensor, and controller. The traveling–standing wave caused by free space microwave multiple reflection is discussed. The moisture content calibration functions eliminated the interference of bulk density and temperature are proposed based on the attenuation of the maximum field strength of the transmission traveling–standing wave. The moisture content of rice, which ranges from 10.75% to 27.62%, is obtained with a standard error of prediction (SEP) of 0.586% and a coefficient of determination ( R2) of 0.988, whereas the moisture content of corn, which ranges from 7.72% to 24.46%, is obtained with a SEP of 0.340% and R2 of 0.991. The main results might provide technical support for the development of accurate and intelligent grain quality detection equipment.

Identification of Fibre Content in Edible Flours Using Microwave Dielectric Cell: Concise Review and Experimental Insights

“…Thus, their recent study focused on the model, which was then used to experiment on cotton seed and wheat grains [59] to observe the microwave attenuation. Another recent valid related study was presented by Li et al [60]. Similar to Nelson [61], the proposed model, however, modified the antenna and used a constantly moving antenna instead, for uniform accuracy of microwave radiation to the sample measured.…”