Amperometric Gas Sensor with Ozone Filter for NO2 and O3 Detection
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Solution Overview
Problem
Current air quality monitoring instruments face challenges in accurately measuring NO2 and O3 at low concentrations due to interference from co-present gases and background drift, requiring a highly accurate, portable, and cost-effective solution for environmental monitoring.
Innovation Solution
An amperometric electrochemical gas sensing apparatus with carbon electrodes and an ozone filter, where the first working electrode measures both NO2 and O3, and the second working electrode measures NO2 after ozone filtration, allowing for accurate differentiation and measurement of O3 concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electrochemical sensor is used to detect multiple gases, then device complexity is reduced, but measurement precision deteriorates due to cross-sensitivity and interference from co-present gases
Solution Approach 1:
The patent divides the detection function into two separate working electrodes: the first working electrode detects both NO2 and O3, while the second working electrode (protected by ozone filter) detects only NO2. This segmentation allows the system to maintain simple overall structure while achieving precise differentiation between gases through comparative measurement.
Solution Approach 2:
The patent introduces an ozone filter as an intermediary component between the gas sample and the second working electrode. This filter selectively removes ozone from the gas phase, allowing the second electrode to measure only NO2, thereby eliminating cross-sensitivity interference while maintaining a relatively simple sensor design.
2Measurement precision
If electrochemical sensors are used for low concentration detection, then sensitivity is improved, but reliability deteriorates due to background drift and interferent gases
Solution Approach 1:
The patent employs a feedback mechanism where the measurements from both working electrodes are continuously compared and processed. The control system uses the difference between the first electrode reading (NO2 + O3) and the second electrode reading (NO2 only) to calculate O3 concentration, providing continuous feedback that compensates for background drift and improves measurement reliability.
Solution Approach 2:
The patent applies preliminary action by using the ozone filter to pre-treat the gas sample before it reaches the second working electrode. This preliminary removal of ozone prevents interference at the detection stage, ensuring more reliable and stable measurements of NO2 at low concentrations without being affected by co-present ozone.
3Measurement precision
If multiple filters are added to remove interferent gases, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by placing the ozone filter specifically at the location of the second working electrode, rather than using multiple filters throughout the system. This localized approach provides the necessary selectivity for NO2 detection while minimizing overall device complexity and maintaining a compact sensor structure.
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 apparatus provides highly accurate measurements of NO2 and O3 over a wide range of concentrations with low cross-sensitivity to interferent gases, ensuring robust and long-term monitoring capabilities while being compact and cost-effective.
Implementation Method 1
a first working electrode which is a carbon electrode and at which both NO 2 and O 3 are reducible to thereby generate a current
Implementation Method 2
a second working electrode which is a carbon electrode and at which NO 2 is reducible to thereby generate a current
Implementation Method 3
an O 3 filter adjacent the second working electrode
Data Source
Figure 1~2(2)
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AI summary
An amperometric electrochemical gas sensing apparatus for sensing NO2 and O3 in a sample gas and a method of using same. The apparatus comprises: a first working electrode which is a carbon electrode and at which both NO2 and O3 are reducible to thereby generate a current; a second working electrode which is a carbon electrode and at which NO2 is reducible to thereby generate a current; and an O3 filter adjacent the second working electrode, and said apparatus is configured such that, in operation, the first working electrode and the O3 filter are exposed to the sample gas in parallel.