Gas Sensor Current Correction for Accurate NOx Measurement
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Solution Overview
Problem
Existing gas concentration measuring apparatuses face challenges in accurately determining the concentration of gas components like NOx in exhaust gases due to differences in electrode materials and manufacturing variations between monitor and sensor cells, leading to inaccuracies in calculating the given gas dependent current.
Innovation Solution
A gas concentration measuring apparatus that includes a gas sensor with a solid electrolyte body and electrodes forming pump, monitor, and sensor cells, where the calculating portion corrects the monitor cell current to approximate the oxygen dependent current, allowing for accurate subtraction from the sensor cell current to derive the given gas dependent current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the monitor cell and sensor cell use different electrode materials (Pt-Au alloy for monitor cell, Pt-Rh alloy for sensor cell), then the sensor cell can detect both oxygen and given gas component (NOx), but the difference in electrode materials and manufacturing variations causes difference between monitor cell current and oxygen dependent current, leading to inaccurate calculation of given gas dependent current
Solution Approach 1:
The patent introduces a correction coefficient as an intermediary factor to bridge the gap between monitor cell current and oxygen dependent current. This correction coefficient, determined through calibration, mediates the relationship between the two currents, allowing accurate calculation of given gas dependent current despite differences in electrode materials and manufacturing variations. The correction coefficient acts as a translator that accounts for the sensitivity differences between cells.
Solution Approach 2:
The patent changes the parameter of electrode sensitivity by introducing a correction coefficient that adjusts the monitor cell current to match the oxygen dependent current. This parameter change compensates for the inherent differences in electrode materials and manufacturing variations, enabling accurate derivation of given gas dependent current while maintaining the functional differences in electrode compositions.
2Ease of operation
If the monitor cell current is directly subtracted from sensor cell current without correction, then the calculation process is simple, but the result is inaccurate due to sensitivity differences and manufacturing variations
Solution Approach 1:
The patent applies preliminary action by determining a correction coefficient through calibration before actual measurement. This pre-established correction factor is then used to adjust the monitor cell current during operation, maintaining calculation simplicity while improving accuracy. The calibration process performed in advance eliminates the need for complex real-time adjustments.
Solution Approach 2:
The patent implements feedback by using the correction coefficient to adjust the monitor cell current based on calibrated reference data. This feedback mechanism ensures that the corrected monitor cell current accurately represents the oxygen dependent current, enabling precise calculation of given gas dependent current while maintaining operational simplicity.
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 approach enhances the accuracy of calculating the concentration of the given gas component by approximating the monitor cell current to the oxygen dependent current, resulting in precise determination of the given gas dependent current and improved measurement accuracy.
Implementation Method 1
a solid electrolyte body which is disposed between the gas chamber and the reference gas chamber and has oxygen ion conductivity
Implementation Method 2
The pump cell is a cell which reduces the concentration of gas
Implementation Method 3
The monitor cell is a cell which detects the concentration of oxygen slightly remaining in the gas whose concentration of oxygen has been reduced by the pump cell
Implementation Method 4
The sensor cell is a cell which measures the sum of concentrations of oxygen and a given gas component (NOx) contained in the gas whose concentration of oxygen has been reduced by the pump cell
Data Source
AI summary
A gas concentration measuring apparatus is provided which works to calculate the concentration of a given gas component with enhanced accuracy. The gas concentration measuring apparatus 1 includes, a gas sensor 10 and a calculating portion 11. The gas sensor 10 is equipped with a pump cell 3, a monitor cell 4, and a sensor cell 5. The calculating portion 11 subtracts a monitor cell current Im that is a current flowing through the monitor cell 4 from a sensor cell current Is that is a current flowing through the sensor cell 5 to calculate the concentration of the given gas component in gas g. When calculating the concentration of the given gas component, the calculating portion 11 performs a correction operation to bring a value of the monitor cell current Im close to a value of an oxygen dependent current Iso that is a component of the sensor cell current Is which arises from the concentration of oxygen.