Feasibility Study of an Industrial Moisture Content Sensor Based on Wheeler Cap

Abstract

The paper proposes a technique for sensing of moisture content of a waste paper block based on Wheeler Cap measurement method. The technique allows sufficient penetration into the sample due to relatively low frequencies in the VHF band. Water blocks within the sample can be detected due to the increased loss compared to a dry sample. The simulation setup comprises a cylindrical Wheeler Cap structure and an electrically small antenna which is located in the same enclosure as the Material Under Test (MUT). The moisture content can be detected due to frequency shift and amplitude change of the reflected signal. The study demonstrates that varying moisture content from 5% to 50% results in the change of the frequency from 276.35 MHz to 264.35 MHz, and simultaneous change in the level of reflected signal from -4.51 to -6.64 dB. Other factors, such as misplacement of the sample, are also discussed.