Gas Sensor Outer Electrode Segmentation for Noise Suppression
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Solution Overview
Problem
Existing gas sensors face difficulties in controlling oxygen concentration in measurement chambers due to transient noise currents caused by changes in oxygen atmospheres, leading to reduced control accuracy.
Innovation Solution
A sensor element with a pump cell and a diffusion resistance portion, where the outer electrode is covered by a porous layer within a hollow space surrounded by a dense layer, maintaining a constant air reference atmosphere and preventing contact with the measurement target gas, thereby suppressing noise currents and maintaining accurate oxygen concentration control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer electrode is directly exposed to the measurement target gas, then the oxygen concentration control function is provided, but transient noise current flows when oxygen atmosphere changes
Solution Approach 1:
The outer electrode structure is segmented into three distinct parts: the electrode body, a porous layer covering the electrode, and a dense layer surrounding the hollow space. This segmentation isolates the electrode from direct contact with measurement target gas while maintaining functional separation between reference atmosphere and measurement gas pathways.
Solution Approach 2:
The porous layer acts as an intermediary between the outer electrode and the measurement target gas, allowing controlled gas interaction while preventing direct contact. The dense layer serves as a second intermediary that completely isolates the electrode from measurement gas and provides structural containment for the hollow space.
2Speed
If the measurement target gas flows quickly into the measurement chamber, then the response time is reduced, but the oxygen concentration control accuracy deteriorates
Solution Approach 1:
The system establishes a stable reference atmosphere in the hollow space surrounding the outer electrode before measurement begins. This preliminary establishment of constant oxygen partial pressure at the electrode interface ensures that even when measurement gas flows rapidly through the measurement chamber, the electrode maintains stable reference conditions for accurate pump current measurement.
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 solution effectively suppresses noise currents and maintains accurate oxygen concentration control, even with changes in oxygen atmospheres, enhancing the control accuracy of the sensor element and preventing electrode material sublimation.
Implementation Method 1
a pump cell including a solid electrolyte 111, an inner electrode 113 formed on a surface of the solid electrolyte 111 and exposed in a measurement chamber 150, and an outer electrode 112 formed on a surface of the solid electrolyte 111 and disposed outside the measurement chamber 150, and configured to adjust an oxygen concentration in the measurement chamber 150 by pumping out and pumping in oxygen in a measurement target gas introduced into the measurement chamber 150
Implementation Method 2
a diffusion resistance portion 151 disposed between outside and the measurement chamber 150 and configured to adjust a diffusion rate of the measurement target gas introduced into the measurement chamber 150
Implementation Method 3
a detection cell 120 configured to measure a concentration of a specific gas in the measurement target gas after the adjustment of the oxygen concentration
Implementation Method 4
The outer electrode is covered by a porous layer and is disposed in a hollow space surrounded by a dense layer that has a gas non-permeable property and that prevents the outer electrode from coming into contact with the measurement target gas
Data Source
AI summary
A sensor element (10) including: a measurement chamber (150); a pump cell (110) including a solid electrolyte (111), an inner electrode (113) exposed to the measurement chamber, and an outer electrode (112), the pump cell being configured to adjust an oxygen concentration in the measurement chamber; a diffusion resistance portion (151); and a detection cell (120) configured to measure a concentration of a specific gas in the measurement target gas after the adjustment of the oxygen concentration. The outer electrode is covered by a porous layer (114) and is disposed in a hollow space (10G) surrounded by a gas non-permeable dense layer 115, 118. The hollow space is in communication with an air introduction hole (10h) that is open on a rear side relative to the diffusion resistance portion. The outer electrode is exposed via the porous layer to air introduced through the air introduction hole.