Cylindrical Microwave Moisture Meter with Rotator
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Solution Overview
Problem
Existing microwave moisture meters for agricultural materials face challenges in achieving high accuracy and repeatability due to variations in measurement caused by the alignment of individual particles and the influence of ionic conduction at low frequencies, which are not adequately addressed by current technologies.
Innovation Solution
A microwave moisture meter assembly with a cylindrical sample holder and a rotator mechanism, combined with antennas that use circular or linear polarization, and an outer holder with matching permittivity to minimize variations in microwave beam alignment and sensitivity, allowing for more precise moisture content measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rectangular sample holder is used with directional antennas for microwave moisture measurement, then the device structure is simple, but the measurement accuracy and repeatability are insufficient due to beam alignment variations
Solution Approach 1:
The patent replaces the rectangular sample holder with a cylindrical sample holder. The cylindrical shape provides rotational symmetry, allowing the microwave beam to pass through the sample regardless of the holder's angular position. This eliminates measurement variations caused by beam alignment with rectangular edges, thereby improving measurement accuracy and repeatability while adding minimal structural complexity.
Solution Approach 2:
The patent introduces a rotator mechanism that rotates the cylindrical sample holder during measurement. This dynamic rotation ensures that the microwave beam passes through multiple orientations of the sample, averaging out any residual variations and further improving measurement repeatability. The rotational motion transforms a static measurement into a dynamic process that captures more comprehensive sample characteristics.
2Reliability
If low frequency electromagnetic waves are used for moisture measurement, then the measurement system is simpler, but ionic conduction influences the dielectric properties and reduces measurement consistency
Solution Approach 1:
The patent changes the frequency parameter of the electromagnetic wave from low frequency to microwave frequency (2.45 GHz). At microwave frequencies, the wavelength is much smaller than the sample dimensions, and ionic conduction effects become negligible. This parameter change eliminates the harmful influence of ionic conduction on dielectric properties, thereby improving measurement consistency and reliability.
3Measurement precision
If the sample holder material has different permittivity from the measured material, then the holder structure is simpler, but variations in microwave beam alignment and sensitivity occur
Solution Approach 1:
The patent selects a sample holder material (polyethylene) whose permittivity closely matches that of the measured agricultural materials. This homogeneity in permittivity reduces refraction and reflection of microwave beams at the holder-sample interface, minimizing measurement variations and improving sensitivity. The holder material is chosen to be electrically similar to the samples, making the holder effectively invisible to the microwave beam.
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
The solution significantly reduces measurement variance and improves sensitivity, achieving higher accuracy and repeatability in moisture content determination, as demonstrated by reduced standard deviation and improved confidence intervals in moisture readings.
Implementation Method 1
a microwave source, the microwave meter assembly configured to measure attenuation and phase changes in a sample of material being measured
Implementation Method 2
the sample holder is comprised of a material that approximates a permittivity of a material being measured that is disposed within the sample holder
Implementation Method 3
a receiving antenna on an opposite side of sample holder directly opposite the transmitting antenna, the receiving antenna configured to receive a transmitted circular polarized microwave through the sample holder
Data Source
AI summary
A microwave moisture sensor for agricultural materials, such as grains and nuts, is disclosed herein that includes a material sample holder having a substantially cylindrical cavity formed therein. The meter assembly further includes a transmitting antenna on a side of the sample holder and a receiving antenna on a side of sample holder directly opposite the transmitting antenna wherein the sample holder is located between the two antennas, the receiving antenna configured to receive a transmitted microwave through the sample holder.