Multi-Pump Gas Sensor for Water Measurement Under CO2 Interference
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Solution Overview
Problem
The measurement accuracy of water concentration in gas sensors is degraded due to the presence of carbon dioxide in the measurement gas.
Innovation Solution
A gas sensor configuration with multiple pump cells and a control device that adjusts oxygen partial pressures and pumps to oxidize hydrogen and carbon monoxide, allowing for the derivation of water concentration by correcting the pump current based on the carbon dioxide concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a gas sensor uses a single pump cell to measure water concentration, then the device complexity is low, but the measurement precision of water concentration is degraded due to carbon dioxide interference
Solution Approach 1:
The sensor divides the measurement function into three separate pump cells, each responsible for a specific task: the first pump cell removes oxygen and reduces water/carbon dioxide, the second pump cell oxidizes hydrogen from water reduction, and the third pump cell oxidizes carbon monoxide from carbon dioxide reduction. This segmentation allows independent measurement of water concentration without interference from carbon dioxide, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent introduces intermediate chambers and electrochemical reactions as mediators between the measurement gas and the detection system. The first chamber acts as an intermediary where oxygen is removed and gases are reduced, the second chamber intermediates the oxidation of hydrogen, and the third chamber intermediates the oxidation of carbon monoxide. These intermediaries enable accurate water concentration measurement by separating the measurement process from carbon dioxide interference.
2Device complexity
If the sensor oxidizes both hydrogen and carbon monoxide in the same chamber, then the device complexity is reduced, but the measurement precision of water concentration cannot be maintained due to overlapping reactions
Solution Approach 1:
The patent segments the oxidation process into two separate chambers: the second chamber exclusively oxidizes hydrogen generated from water reduction, while the third chamber exclusively oxidizes carbon monoxide generated from carbon dioxide reduction. This spatial segmentation prevents reaction interference and enables accurate differentiation between water and carbon dioxide concentrations, resolving the contradiction between device complexity and measurement precision.
Solution Approach 2:
Each pump cell is designed with specific local quality characteristics: the second pump cell is optimized for hydrogen oxidation with appropriate catalysts and oxygen partial pressure conditions, while the third pump cell is optimized for carbon monoxide oxidation. This local optimization ensures that each chamber performs its specific function efficiently without interference from the other gas species, maintaining measurement precision while managing device complexity.
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 accurately measures water concentration by accounting for carbon dioxide interference, enhancing measurement accuracy.
Implementation Method 1
a first pump cell including a first inner electrode disposed in a first chamber of the measurement gas flow path, and a first outer electrode disposed on the outside of the element body
Implementation Method 2
an element body having an oxygen-ion-conductive solid electrolyte layer
Implementation Method 3
a second pump cell including a second inner electrode disposed in a second chamber located downstream of the first chamber of the measurement gas flow path, and a second outer electrode disposed on the outside of the element body
Implementation Method 4
oxidizing hydrogen generated by the reduction of water in the first chamber in the second chamber
Implementation Method 5
a third pump cell including a third inner electrode disposed in a third chamber located downstream of the second chamber of the measurement gas flow path, and a third outer electrode disposed on the outside of the element body
Implementation Method 6
oxidizing carbon monoxide generated by the reduction of carbon dioxide in the first chamber in the third chamber
Data Source
AI summary
A gas sensor includes a sensor element and a control device, and configured to measure a water concentration in a measurement gas, wherein the control device performs: a first pump cell control processing in which oxygen is pumped out from around a first inner electrode; a second pump cell control processing in which oxygen is pumped to around a second inner electrode by controlling the second pump cell; a third pump cell control processing in which oxygen is pumped to around a third inner electrode by controlling the third pump cell; and the control device derives the water concentration in the measurement gas based on the second pump current flowing through the second pump cell by the second pump cell control processing, while taking into account the third pump current flowing through the third pump cell by the third pump cell control processing.