Internal Electrode Humidity Sensor for Corrosive Environments
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Solution Overview
Problem
Current humidity sensors face challenges such as poor accuracy, sensitivity, and susceptibility to water droplets and corrosive gases, which affect their ability to accurately measure humidity, especially when exposed electrodes lead to short circuits and corrosion.
Innovation Solution
The design incorporates internal electrodes covered by a moisture-sensitive member with a dielectric constant that changes with humidity, preventing short circuits and corrosion, and increasing sensitivity by allowing wider water molecule absorption without being blocked by electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the upper electrode is exposed to the surface to simplify the structure, then the device complexity is reduced, but the reliability deteriorates due to water droplet adhesion causing short circuits and corrosion
Solution Approach 1:
The patent embeds the first and second electrodes internally within the humidity sensor material, nesting them between the upper and lower surfaces. This internal electrode configuration protects the electrodes from direct exposure to water droplets and corrosive gases, preventing short circuits and corrosion while maintaining structural simplicity through the natural encapsulation provided by the humidity sensor material itself.
2Quantity of substance
If the thickness of the humidity sensor material is reduced to increase capacitance, then the capacitance increases, but the reliability deteriorates due to increased short circuit risk from water droplet adhesion
Solution Approach 1:
By nesting the electrodes internally within the humidity sensor material rather than exposing them on the surface, the patent eliminates the direct pathway for water droplets to cause short circuits. This allows the use of thinner humidity sensor material to increase capacitance without compromising reliability, as the internal electrode configuration provides inherent protection against water-induced short circuits regardless of material thickness.
3Area of stationary object
If the upper electrode is exposed to increase the electrode area, then the capacitance increases, but the measurement precision deteriorates due to water droplet interference with the sensing mechanism
Solution Approach 1:
The internal embedding of electrodes within the humidity sensor material protects the electrode-humidity sensor material interface from water droplet contamination. This ensures that the capacitance change mechanism remains unaffected by water-induced resistance changes or electrode area modifications, maintaining measurement precision while still allowing sufficient electrode area for adequate capacitance through the internal configuration.
4Volume of moving object
If the resonance frequency is lowered to reduce microcomputer clock frequency and module size, then the device size is reduced, but the manufacturing precision becomes more difficult due to increased sensitivity to parasitic capacitance
Solution Approach 1:
The internal electrode configuration minimizes exposed electrode surfaces that could generate parasitic capacitance, thereby reducing the overall parasitic capacitance in the resonance circuit. This allows the system to operate at lower resonance frequencies with improved frequency stability, enabling the use of lower-clock-frequency microcomputers and smaller module sizes without sacrificing manufacturing precision or frequency accuracy.
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 configuration enhances sensitivity and accuracy by preventing short circuits and corrosion, allowing for reliable humidity measurement even in the presence of corrosive gases and improving the capacitance and resonance frequency characteristics.
Implementation Method 1
a moisture-sensitive member with a dielectric constant changing in accordance with humidity
Implementation Method 2
The capacitance change type humidity sensor measures a change in capacitance when water is drawn into these materials, to measure the relative humidity in the atmosphere
Data Source
AI summary
A humidity sensor is provided with a first electrode electrically connected to a first terminal, and a moisture-sensitive member. The first electrode may include a first internal electrode unit. The first internal electrode unit may include a first main surface covered with the moisture-sensitive member, and a second main surface covered with the moisture-sensitive member. The humidity sensor may further include a second electrode electrically connected to the second terminal. The second electrode may include a second internal electrode unit. The second internal electrode unit may include a third main surface covered with the moisture-sensitive member, and a fourth main surface covered with the moisture-sensitive member. The first internal electrode unit may include a portion facing at least a part of the second internal electrode unit across the moisture-sensitive member.