Carbon Monoxide Sensor Hydrogen Cross Sensitivity Reduction
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Solution Overview
Problem
Existing carbon monoxide sensors exhibit high or variable levels of hydrogen cross sensitivity due to mismatched catalysts, affecting their stability and accuracy over time.
Innovation Solution
A carbon monoxide sensor design featuring a housing with a gas entry hole and electrical terminals, where the first and second electrodes have a membrane with a layer of platinum black catalyst, with the second electrode having a lower amount of catalyst than the first, and a separator between them, minimizing cross sensitivity by careful catalyst pairing and specific dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mismatched catalysts are used in the electrodes to ensure stability, then the sensor can maintain potential stability throughout its life, but hydrogen cross sensitivity becomes high and variable
Solution Approach 1:
The patent changes the critical parameter of catalyst matching by ensuring both the sensing electrode and counter electrode use platinum black catalyst with matched surface areas. This parameter change resolves the contradiction by eliminating the catalyst mismatch that causes hydrogen cross sensitivity while maintaining potential stability throughout the sensor's operational life.
Solution Approach 2:
The patent applies homogeneity by using the same type of catalyst (platinum black) on both electrodes with matched surface areas. This creates a homogeneous catalyst system that eliminates the variability and high hydrogen cross sensitivity caused by mismatched catalysts, while maintaining the stability required for reliable operation.
2Duration of action of stationary object
If the sensor is designed to be maintenance free and stable for long periods, then it achieves long-term operational stability, but hydrogen cross sensitivity varies depending on catalyst batches
Solution Approach 1:
The patent changes the catalyst specification parameter to require matched surface areas for both electrodes. This ensures that regardless of catalyst batch variations, the sensor maintains measurement precision by eliminating the catalyst mismatch that causes hydrogen cross sensitivity, while achieving long-term operational stability.
Solution Approach 2:
The patent uses identical catalyst types (platinum black) on both electrodes with matched surface areas, creating a replicated catalyst configuration. This copying approach ensures consistency across different catalyst batches, maintaining measurement precision while achieving long-term operational stability.
3Reliability
If different catalysts are used on sensing and counter electrodes, then enough stability of potential is achieved, but subtle differences in catalyst behavior cause hydrogen cross sensitivity
Solution Approach 1:
The patent applies homogeneity by using the same catalyst material (platinum black) on both the sensing electrode and counter electrode. This eliminates the subtle behavioral differences between mismatched catalysts that cause hydrogen cross sensitivity, while maintaining potential stability through the matched surface area design.
Solution Approach 2:
The patent changes the catalyst selection parameter from using different catalysts to using matched platinum black catalysts with equal surface areas. This parameter change eliminates the harmful subtle differences in catalyst behavior while preserving the potential stability required for reliable sensor operation.
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 sensor effectively reduces hydrogen cross sensitivity, providing a direct and stable measurement of carbon monoxide concentration with improved long-term stability and accuracy.
Implementation Method 1
Gas diffusing into the sensor is either oxidized or reduced at the sensing electrode and, coupled with a corresponding counter reaction at the other electrode, a current is generated through the external circuit
Implementation Method 2
First and second electrodes in the housing interior space each comprises a membrane having a layer of platinum black catalyst on one side
Implementation Method 3
Since the rate of gas entering into the sensor is controlled by the capillary diffusion barrier, the current generated is proportional to the concentration of gas present outside the sensor
Data Source
AI summary
A gas sensor in one form comprises a housing including a base and a top defining an interior space. The housing includes a gas entry hole and first and second electrical terminals. First and second electrodes in the housing interior space each comprise a membrane having a layer of platinum black catalyst on one side. The second electrode includes a lower amount of platinum black catalyst than the first electrode. A separator is placed between the first and second electrodes. Current collectors electrically connect the first and second electrodes to the respective first and second electrical terminals whereby sensor current represents concentration of gas while minimizing cross sensitivity.