NOx Sensor Pumping Current Measurement for Dynamic Exhaust
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Solution Overview
Problem
Existing methods for determining ammonia and nitrogen monoxide concentrations in motor vehicle exhaust gas streams are not accurate during dynamic vehicle operation, as they fail to account for variations in concentrations within short time frames.
Innovation Solution
A nitrogen oxide sensor with three chambers connected via diffusion pathways, operating in two modes, measures successive pumping current values to accurately calculate ammonia and nitrogen monoxide concentrations using a control unit that processes these measurements according to specific relationships, ensuring precise concentration determination even during dynamic operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single pumping current measurement is used to determine ammonia and nitrogen monoxide concentrations, then the measurement process is simple, but the measurement precision is insufficient during dynamic vehicle operation
Solution Approach 1:
The sensor alternates between two modes of operation (first mode and second mode) in a periodic manner, taking successive pumping current measurements at different time points. This periodic switching allows the system to capture concentration variations during dynamic vehicle operation while maintaining measurement accuracy through multiple samples.
Solution Approach 2:
The sensor system dynamically switches between different operational modes depending on the measurement requirements. The control unit adapts the sensor operation between first mode (with first diffusion pathway) and second mode (with second diffusion pathway) to handle varying exhaust gas conditions during vehicle operation, enabling accurate real-time concentration determination.
2Measurement precision
If successive pumping current measurements in different modes of operation are taken, then measurement precision is improved, but the measurement time increases
Solution Approach 1:
The sensor continuously takes pumping current measurements in successive modes without interruption, maintaining continuous monitoring of exhaust gas concentrations. The control unit processes these continuous measurements to determine ammonia and nitrogen monoxide concentrations in real-time, ensuring that the system remains responsive to dynamic vehicle operation conditions.
3Measurement precision
If the sensor operates in a single mode, then the device complexity is reduced, but the ability to determine individual concentrations accurately is compromised
Solution Approach 1:
The sensor is divided into multiple functional chambers (first chamber, second chamber, third chamber) with separate diffusion pathways that can be independently activated. This segmentation allows the system to perform different measurement functions in different modes, enabling accurate determination of individual ammonia and nitrogen monoxide concentrations through selective activation of specific chambers and pathways.
Solution Approach 2:
The sensor system is designed with multi-functionality, where the same sensor structure can operate in multiple modes (first mode and second mode) to perform different measurement tasks. This universal design allows the sensor to determine both ammonia and nitrogen monoxide concentrations accurately while using a single integrated sensor unit, avoiding the need for separate sensors for each gas component.
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 allows for accurate and individual determination of ammonia and nitrogen monoxide concentrations in motor vehicle exhaust gas streams, even during dynamic operation, by leveraging the differential pumping current values measured in different modes of operation, thereby enhancing measurement precision.
Implementation Method 1
the ammonia present in the exhaust gas stream is converted to nitrogen monoxide therein
Implementation Method 2
Nitrogen monoxide is converted therein to nitrogen and oxygen, and a pumping current is measured
Implementation Method 3
each connected to one another by a diffusion pathway
Data Source
AI summary
Various embodiments include a method of ascertaining the ammonia concentration and the nitrogen monoxide concentration in the exhaust gas stream from a motor vehicle comprising: measuring a pumping current at least three times; and determining an ammonia concentration and a nitrogen monoxide concentration based on three successive pumping current measurements.