A Novel, Portable and Fast Moisture Content Measuring Method for Grains Based on an Ultra-Wideband (UWB) Radar Module and the Mode Matching Method

Abstract

To perform fast and portable grain moisture measurements under field conditions, a novel moisture sensor was designed, which consisted of a coaxial waveguide, a circular waveguide, and an isolation layer. The electromagnetic characteristics of the sensor were simulated and measured. The analytical model, which represented the relationship between the reflection coefficient of the sensor and the complex permittivity of grain, was established by using the mode matching method. The reflection coefficient of the sensor was measured by using an ultra-wideband (UWB) radar module, and the moisture content of grains was calculated from the complex permittivity by using density-independent model. To verify the performance of the proposed method, wheat, rough rice, and barley were taken as examples. The measured results in the range from 1.0% to 26.0%, wet basis, agreed well with the reference values (R2 was more than 0.99), and the maximum absolute errors for wheat, rough rice, and barley were 1.1%, 1.0%, and 1.4%, respectively. In addition, the effect of isolation layer was discussed. Both the simulation results and the experimental results showed that the isolation layer improved the stability of sensor.

New Sensing Technologies for Grain Moisture

“…Agriculture 2022, 11, x FOR PEER REVIEW 6 Infrared thermography (IR) [35] Detect difference in IR emitted by a dry sam and a wet sample Infrared spectroscopy [32,36,37] Analysis of radiation absorption in the infra spectrum Hyperspectral imaging (HSI) [38,39] Evaluates drying kinetics of the drying met Equilibrium relative humidity (ERH) [40][41][42] Determines the humidity as a function of th tio between the EMC and ERH value at fix temperature…”

“…This method allows a broadband electrical signal to be emitted in a cylindrical vessel and the reflection coefficient of the sensor and the complex permittivity of the grain are studied using formulations [32]. The sensor reflection coefficient was measured using an ultra-wideband radar module (UWB) and the moisture content of the grains was calculated from the complex permittivity using a density-independent model [33].…”

“…Magnetic resonance [29][30][31] Analysis of free-induction decay (FID) and, in some cases, spin echo (SE) outputs Ultra-wideband (UWB) radar method [32,33] Reflection coefficient of the sensor and the complex permittivity of the grain are analyzed Ultrasonic (Acoustic Method) [34] Analysis and comparison of the incident sound wave in grains at frequencies from 5 to 50 kHz…”

“…This technique is based on the analysis of the near infrared (NIR) spectrum, it allows the simultaneous analysis of the micro components of the product. This rapid and nondestructive technique determines the main components from the radiation spectra emitted by the product [32]. Specific organic molecules absorb wavelengths of near-infrared The measurement principle is based on detecting the difference in the a dry and a wet sample.…”

Low-Cost Lens Antenna Design for Microwave Moisture Detection

“…Online measurement of moisture has become an urgent problem to be solved in the eld of food production [1,2]. e development of moisture sensors based on the microwave free-space method is presently a popular research direction.…”