Carbon Monoxide Sensor Humidity Control
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Solution Overview
Problem
Existing carbon monoxide sensors face challenges in maintaining sensor lifespan due to water loss and sensitivity changes caused by humidity fluctuations, and they often require expensive noble metal parts and are prone to corrosion.
Innovation Solution
A carbon monoxide sensor design featuring a solid ion conducting electrolyte membrane with gas diffusion layers and a permeation barrier to control gas and water entry, using a polymer electrolyte membrane with platinum/carbon electrodes and a semi-permeable permeation barrier to manage humidity and extend sensor lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a water reservoir is used to maintain electrolyte function, then sensor reliability is improved, but water loss through the gas entry hole limits sensor lifespan
Solution Approach 1:
A hydrophobic coating is applied to the gas entry hole to create an intermediary barrier that selectively allows gas molecules to pass while blocking water molecules. This coating acts as a mediator between the gas entry requirement and water loss prevention, enabling the sensor to maintain its water reservoir function without excessive water evaporation, thereby extending sensor lifespan while preserving reliability
2Reliability
If atmospheric humidity is used to replenish electrolyte water, then sensor reliability is improved, but acid concentration changes and sensor bursting occurs in high humidity
Solution Approach 1:
The hydrophobic coating on the gas entry hole serves as a selective barrier that mediates between atmospheric humidity and the electrolyte. It allows controlled gas exchange while preventing uncontrolled water vapor ingress that would dilute the acid concentration, thereby maintaining electrolyte composition stability while still providing sufficient humidity for reliable operation
Solution Approach 2:
The invention changes the physical-chemical parameter of the gas entry hole by applying a hydrophobic coating, which alters its permeability characteristics. This parameter change enables selective transport properties where gas molecules can pass but water molecules are blocked, stabilizing the electrolyte composition against humidity-induced concentration changes
3Reliability
If noble metal internal parts are used in acid-based sensors, then sensor reliability is improved, but manufacturing cost increases
Solution Approach 1:
The invention replaces expensive noble metal components with less costly alternative materials that can be used in an acid-based sensor environment. By selecting materials that are corrosion-resistant but not necessarily noble metals, the design achieves adequate reliability at reduced manufacturing cost, effectively substituting expensive long-lasting materials with cheaper materials that meet the operational requirements
4Reliability
If acid-based electrolyte is used, then sensor reliability is improved, but corrosion problems occur
Solution Approach 1:
The invention replaces noble metal materials with less expensive alternative materials that are selected for their corrosion resistance in acid environments. These alternative materials maintain sufficient reliability for sensor operation while eliminating the corrosion issues associated with noble metals and reducing manufacturing costs
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 design effectively controls gas entry and humidity, reducing water loss and sensor sensitivity variations, leading to a longer-lasting sensor with reduced costs and minimized corrosion risks, while maintaining sensitivity to carbon monoxide levels.
Implementation Method 1
gas diffusion capillary transport construction for controlling the gas entry to the sensor
Implementation Method 2
water permeation barrier for controlling the transport of water vapor from the water reservoir to the main sensor cell
Implementation Method 3
electrochemical sensors for toxic and combustible gases sense the presence of the target gas by either an electrochemical oxidation or reduction process at a catalytic electrode surface
Implementation Method 4
electrochemical oxidation or reduction process at a catalytic electrode surface
Data Source
AI summary
A gas sensor having first and second electrodes, an ion conducting solid electrolyte membrane positioned therebetween, first and second electrically conductive gas diffusion layers, first and second electrode contact members for electrically coupling said first and second electrodes to an external circuit, a water reservoir, a gas entry passageway and a water permeation barrier for controlling the transport of water vapor to the ion conducting solid electrolyte membrane. The water permeation barrier is a thin walled member which allows water vapor to diffuse therethrough and evaporate from an exit surface, the thickness of the water permeation barrier controlling the internal relative humidity of the sensor. A method for adjusting the present sensor in-situ due to changes in the current humidity conditions of the sensor so as to keep the gas sensitivity loss within a predetermined range is also disclosed.