Leak Detection Zero Function Signal Dithering Control
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Solution Overview
Problem
Current leak detection methods using mass spectrometry face challenges in accurately determining low leak rates due to interference from water and contamination, leading to false negatives when the background signal noise masks the detection signal, and the zero function can inadvertently set a low leak rate indication, potentially missing critical leaks.
Innovation Solution
The method involves determining and evaluating signal dithering to set a lower indication limit or trigger value, ensuring the zero function is only enabled when the signal stability meets the desired sensitivity, preventing false negatives and ensuring reliable leak rate measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the zero function is used to set the background signal to zero, then the measurement sensitivity is improved, but false negatives occur when the background signal noise masks the detection signal
Solution Approach 1:
The system performs preliminary evaluation of signal dithering (signal stability) before enabling the zero function. This preliminary action ensures that the background signal is sufficiently stable and free from masking noise before attempting to set it to zero, preventing false negatives while maintaining sensitivity.
Solution Approach 2:
The system continuously monitors signal dithering and uses this feedback to dynamically control the zero function. When signal dithering exceeds a threshold indicating instability or noise masking, the zero function is blocked, providing feedback-based protection against false negatives while allowing sensitive measurements when conditions are favorable.
2Measurement precision
If the zero function is enabled to remove background signal, then the leak rate measurement accuracy is improved, but the device complexity increases due to additional evaluation requirements
Solution Approach 1:
The system uses the mass spectrometer's own signal processing capabilities to evaluate signal dithering and control the zero function. The existing analog-to-digital converter and signal processing units perform the dithering evaluation without requiring separate dedicated hardware, allowing the system to self-regulate while minimizing additional complexity.
3Reliability
If the lower indication limit is set to filter out noise, then the false positive rate is reduced, but the detection sensitivity for small leaks is decreased
Solution Approach 1:
The lower indication limit is not fixed but dynamically adjusted based on real-time signal dithering evaluation. When signal stability deteriorates due to noise or contamination, the limit is automatically raised to prevent false positives. When signal quality improves, the limit is lowered to maintain high sensitivity for small leaks, creating a dynamic balance between reliability and precision.
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 safety and accuracy of leak detection by ensuring that only valid leak rates above the set sensitivity are indicated, preventing unnoticed leaks and providing reliable measurements.
Implementation Method 1
The smaller the leak rate, the higher the demands regarding purity and final vacuum. In local leak detection, a vacuum pump evacuates the container until the test pressure required for the leak detector is reached.
Implementation Method 2
Test gas entering the container is pumped off by the vacuum pump and detected by a mass spectrometer.
Data Source
AI summary
In leak detection, the signal generated by a test gas is superposed by interferences which fade as the vacuum generation in a container proceeds. Depending on the negative slope of the volume signal (MS), a lower indication limit (AG) is calculated. Upon activation of a zero function, the volume signal (MS) is not reduced to zero but only to the level of the indication limit (AG). Any exceeding of the indication limit is identified as a leak. Thus, the maximum sensitivity of the leak detection is guaranteed at any time.