Multi-frequency Microwave Sensor for Temperature-Independent Moisture Measurement
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Solution Overview
Problem
Existing microwave sensors for measuring moisture in cellulose-based products, such as paper and wood chips, require independent temperature measurements due to temperature sensitivity, limiting their accuracy and requiring additional sensors for basis weight measurement.
Innovation Solution
A microwave sensor that measures the reflection or transmission transfer function of microwaves at various frequencies to characterize moisture and temperature without needing separate temperature measurements, using a calibration model to extract moisture and temperature from the transfer function, allowing for accurate moisture measurement in cellulose-based products without temperature correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resonant-cavity microwave technique is used to measure moisture, then measurement sensitivity to water content is improved, but temperature sensitivity increases requiring independent temperature measurement
Solution Approach 1:
The patent segments the measurement process into multiple frequency points (at least two different frequencies). By measuring at multiple frequencies and analyzing the frequency response, the system can distinguish between moisture effects and temperature effects, eliminating the need for separate temperature measurement while maintaining moisture measurement accuracy.
Solution Approach 2:
The patent changes the microwave frequency parameter to resolve the temperature sensitivity problem. By measuring at different frequencies and observing how the resonance characteristics change, the system can decouple temperature effects from moisture effects, achieving temperature-independent moisture measurement without additional sensors.
2Measurement precision
If resonant-cavity microwave technique is used, then moisture measurement accuracy is improved, but additional sensors and correction algorithms are required
Solution Approach 1:
The patent makes the microwave sensor multi-functional by using it to obtain both moisture content and temperature information through frequency response analysis. The same sensor system that measures moisture also provides temperature data, eliminating the need for separate temperature sensors and correction algorithms.
Solution Approach 2:
The patent uses feedback from the frequency response characteristics to automatically compensate for temperature effects. By continuously monitoring the resonance frequency shifts and using this information to adjust the moisture measurement calculation, the system achieves accurate moisture measurement without external temperature correction.
3Device complexity
If single frequency microwave measurement is used, then device simplicity is maintained, but temperature independence is lost
Solution Approach 1:
The patent segments the frequency spectrum into multiple measurement points. By using at least two different frequencies, the system gains the ability to distinguish temperature effects from moisture effects while maintaining relative system simplicity. This segmentation approach provides temperature independence without requiring complex additional hardware.
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
Enables accurate, temperature-independent moisture measurement in cellulose-based products, eliminating the need for separate temperature sensors and providing both moisture and temperature data, improving production yield and product quality by directly measuring moisture content and temperature from the microwave transfer function.
Implementation Method 1
The microwave sensor directly measures the reflection or transmission of microwaves at a number of frequencies so as to characterize the reflection or transmission transfer function of the product under test
Implementation Method 2
In this range the dielectric properties of water change dramatically. Measurements must be made in this range such that the measured reflection or transmission function of the sample is sensitive to water content as well as to the sample's temperature
Data Source
AI summary
Microwave techniques for measuring moisture and other properties of paper and related products without requiring an independent measurement of temperature are provided. A sensor directly measures the reflection or transmission of microwaves at a number of well-chosen frequencies so as to characterize the absorption spectrum of the product. The technique of measuring the parameters of a composition includes: (a) directing incident microwave radiation over a spectrum of wavelengths from an antenna upon the composition; (b) measuring the microwave radiation over the spectrum of wavelengths that emerges from the composition; (c) determining the reflected and/or transmitted transfer function; and (d) relating the transfer function of the composition to the parameters of the composition by applying a theoretic, calibrated, or hybrid model. The product moisture and temperature are extracted from the transfer function.