Oxygen Sensor Calibration via Test Gas Valves
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Solution Overview
Problem
Closed-cycle breathing apparatuses face reliability issues with oxygen sensors due to calibration errors, sensor failures, and condensation, which can lead to inaccurate oxygen partial pressure readings, posing risks of hyperoxia or hypoxia during dives.
Innovation Solution
An oxygen control system with two sensors and three electronically controlled gas valves, using automated active testing and monitoring, including periodic validation with pure oxygen and diluent gases to ensure accurate calibration and detection of sensor failures, and a secondary sensor for redundancy and leak detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If automated active testing and monitoring with multiple sensors is implemented, then reliability is improved, but device complexity increases
Solution Approach 1:
The system divides the monitoring function into multiple independent oxygen sensors (primary and secondary) that operate separately but are integrated into a unified control system. Each sensor can be independently tested and validated, allowing the system to maintain high reliability through distributed sensing while managing complexity through modular architecture
Solution Approach 2:
The control system continuously monitors oxygen sensor readings and compares them against expected values derived from fitted calibration curves. When deviations are detected, the system automatically triggers validation procedures using test gas supplies, creating a closed-loop feedback mechanism that maintains sensor reliability without requiring constant manual intervention
Solution Approach 3:
The system performs self-validation by using its own test gas supplies (pure oxygen and diluent gases) to automatically recalibrate and verify sensor accuracy during operation. This self-service capability allows the system to maintain reliability without external calibration equipment, reducing operational complexity while ensuring continuous sensor accuracy
2Measurement precision
If periodic validation with pure oxygen and diluent gases is performed, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The system performs calibration and validation procedures before the actual diving operation begins. By completing sensor calibration against known gas concentrations and validating measurement accuracy in advance, the system ensures measurement precision is established beforehand, allowing uninterrupted diving operation without time loss during the dive
Solution Approach 2:
Validation is performed periodically at predetermined intervals or when specific conditions are met (such as depth changes or oxygen concentration thresholds). This periodic validation maintains measurement precision without requiring continuous testing, optimizing the balance between accuracy and time efficiency by validating only when necessary
3Reliability
If a secondary oxygen sensor is used for redundancy, then reliability is improved, but device complexity increases
Solution Approach 1:
The system uses a secondary oxygen sensor that replicates the measurement function of the primary sensor. This copy provides redundant measurement capability without requiring a completely separate independent system, reducing complexity while maintaining reliability through functional duplication
Solution Approach 2:
The primary and secondary oxygen sensors are integrated into a single control system that processes readings from both sensors together. The control system combines data from multiple sensors to determine actual oxygen partial pressure, merging their functions to achieve reliability through redundancy while managing complexity through unified processing
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 system provides reliable oxygen control by minimizing calibration errors and sensor failures, ensuring safe oxygen levels during dives, and reducing the risk of hyperoxia or hypoxia, thereby enhancing diver safety.
Implementation Method 1
at least one primary oxygen sensor arranged to operatively measure the oxygen in the breathing loop
Implementation Method 2
at least a secondary oxygen sensor arranged to operatively measure the oxygen in the breathing loop
Implementation Method 3
A test channel arrangement adapted to operatively provide a first gas having a first fraction of oxygen from a first gas supply to said primary oxygen sensor
Implementation Method 4
At least a first test valve arrangement arranged to operatively open and close the flow of said first gas through said test channel arrangement
Implementation Method 5
The control arrangement is arranged to operatively actuate said first test valve arrangement so as to provide an amount of said first gas to said primary oxygen sensor
Implementation Method 6
The control arrangement is arranged to operatively obtain measures from said primary and secondary oxygen sensors
Data Source
Figure 1
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Figure 3a
AI summary
The invention is directed to an oxygen sensor arrangement (8) and a method for operating such an arrangement for sensing the oxygen in a breathing loop (29) of a breathing apparatus. The sensor arrangement comprises : at least one primary oxygen sensor (30) arranged to operatively measure the oxygen in the breathing loop (29), at least a secondary oxygen sensor (31) arranged to operatively measure the oxygen in the breathing loop (29), and a control arrangement (40) for obtaining measures from said oxygen sensors. A test channel arrangement (15, 48) is adapted to operatively provide a first gas having a first fraction of oxygen from a first gas supply (16) to said primary oxygen sensor (30) at a position (267) adjacent to said primary oxygen sensor (30). At least a first test valve arrangement (41, 42) is arranged to operatively open and close the flow of said first gas through said test channel arrangement (15, 48). Said control arrangement (40) is arranged to operatively actuate said first test valve arrangement (41, 42) so as to provide an amount of said first gas to said primary oxygen sensor (30) via said test channel arrangement (15, 48). Said control arrangement is arranged to operatively obtain measures from said primary (30) and secondary (31) oxygen sensors.