Microwave Humidity Sensor Using Cavity Resonance
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Solution Overview
Problem
Existing methods for measuring moisture in building components are inefficient and lack accuracy, particularly in determining relative humidity and moisture content in hygroscopic materials.
Innovation Solution
A humidity sensor with an electromagnetically shielding sensor housing and a strip conductor, using coaxial cables to conduct microwaves, and a moisture-storing material inside the housing to establish humidity balance, allowing for precise determination of ambient humidity by measuring resonance frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If equilibrium moisture measurement methods are used to detect moisture contamination in building components, then moisture content can be determined, but the measurement precision and accuracy are insufficient
Solution Approach 1:
The patent replaces traditional mechanical/equilibrium moisture measurement methods with electromagnetic wave-based measurement. A microwave resonator generates electromagnetic waves that interact with water molecules in the material, and the resonance frequency shift and quality factor changes provide precise moisture content determination without relying on equilibrium assumptions.
Solution Approach 2:
The patent utilizes changes in electromagnetic parameters (resonance frequency and quality factor) in response to moisture content variations. By measuring how these parameters change when electromagnetic waves interact with moisture in the material, the system achieves high-precision moisture detection through parameter correlation rather than equilibrium measurement.
2Measurement precision
If microwave resonator methods are used to measure moisture content, then measurement accuracy improves, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent designs the sensor housing to serve multiple functions simultaneously: it acts as the microwave resonator cavity, provides electromagnetic shielding, and serves as the sensor housing structure. This multi-functionality reduces the number of separate components needed and simplifies manufacturing while maintaining measurement accuracy.
Solution Approach 2:
The patent extracts and integrates only the essential functional elements into a compact sensor head: the resonator cavity, shielding, and measurement electronics are combined in a single integrated unit that can be easily attached to building components, reducing overall system complexity while preserving measurement capabilities.
3Device complexity
If traditional humidity sensors are used for moisture measurement, then the structure is simple, but the sensitivity and measurement capability in hygroscopic materials are insufficient
Solution Approach 1:
The patent replaces traditional mechanical humidity sensing elements with electromagnetic wave interaction. The microwave resonator detects moisture through electromagnetic field interactions with water molecules, providing high sensitivity without complex mechanical or chemical sensing structures.
Solution Approach 2:
The patent utilizes electromagnetic resonance - a form of oscillation at specific frequencies - to detect moisture. The microwave resonator operates at resonant frequencies that are sensitive to moisture content, allowing highly sensitive detection through frequency and amplitude measurements without complex mechanical vibration mechanisms.
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 and cost-effective measurement of humidity in building materials, suitable for continuous or intermittent monitoring, with high sensitivity and simplicity in manufacturing and installation.
Implementation Method 1
The sensor housing (1) is configured as a cavity resonator with a resonant frequency within the predetermined frequency band
Implementation Method 2
an electromagnetically shielding sensor housing and a strip conductor arranged therein
Implementation Method 3
a moisture-storing material introduced into the housing to establish humidity balance
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a humidity sensor (10) comprising an electromagnetically shielding sensor housing (1) and a strip conductor (4) arranged therein, as well as at least one coaxial cable (3, 5) with an inner conductor (3A, 5A) electrically connected to the strip conductor (4) and an outer conductor (3B, 5B) electrically connected to the sensor housing (1), wherein the strip conductor (4) and the at least one coaxial cable (3, 5) are configured for transmitting microwaves with a frequency (f) in a frequency band (Δf) which covers at least a sub-range of the microwave range between 10 megahertz (MHz) and 300 gigahertz (GHz), wherein the sensor housing (1) is configured as a cavity resonator with a resonant frequency (fR1, fR2, fR3) within the frequency band (Δf) and is shielding for the frequency band (Δf) and has openings (2).which establish sufficient hygroscopic contact between the interior and the environment (U) of the sensor housing (1) for moisture equalization, and wherein moisture-storing material is introduced into the interior of the sensor housing (1). Furthermore, the invention relates to a method for measuring moisture using such a moisture sensor (10) and a method for manufacturing a component comprising such a moisture sensor (10).