Single-Frequency Microwave Sensor for Grain Density and Moisture
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Solution Overview
Problem
Current microwave moisture measurement systems for granular or particulate materials face challenges in accurately determining bulk density and moisture content due to density fluctuations, often requiring secondary measurements or limited frequency ranges, which complicates and costs industrial processes like grain trading and agriculture.
Innovation Solution
A microwave sensor operating at a single frequency with a novel phase-correction algorithm that calculates the real and imaginary parts of complex permittivity from attenuation and phase shift measurements, allowing for instantaneous and nondestructive determination of bulk density and moisture content, independent of density variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If free-space microwave measurement techniques are used for moisture content determination, then nondestructive and contactless measurement is achieved, but bulk density fluctuations in particulate materials produce significant errors in moisture content determination
Solution Approach 1:
The patent changes the measurement approach by introducing a second microwave frequency parameter alongside the first frequency. By measuring both the first frequency (f1) and second frequency (f2) and their respective phase shifts, the system can calculate density-independent moisture content while compensating for bulk density fluctuations. This multi-parameter approach resolves the contradiction by maintaining nondestructive measurement while improving precision through frequency diversity.
Solution Approach 2:
The patent uses the ratio of phase shifts at different frequencies as an intermediary parameter to eliminate density effects. The phase shift ratio serves as a mediator that cancels out the influence of bulk density variations, allowing direct determination of moisture content without separate density measurements. This intermediary approach maintains the nondestructive nature of microwave measurement while correcting for density-induced errors.
2Measurement precision
If mechanical means are used to keep layer thickness constant or use a vibrator to maintain average density, then bulk density fluctuations are reduced, but unpredictable errors remain due to density effect and additional equipment is required
Solution Approach 1:
The patent extracts the density measurement function from the moisture measurement system by using a separate second frequency measurement. Instead of mechanically controlling density with vibrators or layer thickness control devices, the system independently measures density effects through the second frequency phase shift and mathematically separates it from the moisture content calculation. This extraction eliminates mechanical complexity while maintaining measurement precision.
Solution Approach 2:
The patent replaces mechanical density control systems (vibrators, layer thickness control mechanisms) with an electromagnetic field-based solution. By using the ratio of phase shifts at two different frequencies, the system substitutes mechanical density maintenance with an electrical measurement approach that inherently compensates for density variations without requiring additional mechanical equipment.
3Measurement precision
If separate density measurement methods such as gamma-ray attenuation or weighing are used, then density can be determined, but additional cost and technical complications are introduced
Solution Approach 1:
The patent merges the moisture content measurement and density determination into a single integrated microwave measurement system. By simultaneously measuring phase shifts at two different frequencies through the same microwave path, the system combines what would traditionally require separate gamma-ray or weighing measurements into one unified measurement process. This merging eliminates additional equipment and reduces system complexity while maintaining precision for both parameters.
Solution Approach 2:
The patent creates a universal microwave measurement system that performs multiple functions: it simultaneously determines moisture content, bulk density, and their interaction effects through a single measurement configuration. The dual-frequency phase shift measurement serves multiple purposes, eliminating the need for separate dedicated density measurement devices like gamma-ray attenuators or scales, thereby reducing overall system complexity and cost.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides accurate, real-time, and cost-effective monitoring of moisture content and bulk density, reducing errors and operational complexities in industrial processes, particularly in grain and peanut handling, by using a single-frequency microwave circuit and phase correction algorithm.
Implementation Method 1
Electromagnetic wave-interaction-based techniques meet this requirement and provide a tool for continuous measurement
Implementation Method 2
The dielectric properties of materials are intrinsic properties usually expressed as the relative complex permittivity: ε=ε′−jε′′ where ε′ is the dielectric constant
Implementation Method 3
measurement of the attenuation and phase shift of a microwave signal after it has traversed the sample material
Data Source
AI summary
A microwave sensor and algorithm for instantaneous and nondestructive determination of bulk density and moisture content in granular or particulate materials at a single microwave frequency, especially agricultural commodities, which uses an inexpensive microwave circuit for determining the real and imaginary parts of relative complex permittivity using an algorithm for phase correction.