Smoke Detector External Sampling Dual-Wavelength Ambient Light Correction
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Solution Overview
Problem
Smoke detectors with external sampling volumes face challenges in distinguishing smoke particles from ambient light and nuisance particles, leading to false alarms or missed fire detections due to difficulties in isolating scattered light signals.
Innovation Solution
Incorporating a proximity sensor with light emitters and detectors, along with an ambient-light sensor, to emit and measure light signals across different wavelengths, allowing for the differentiation of smoke particles from nuisance particles and obstructions by analyzing signal ratios and thresholds, while compensating for ambient light interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an external sampling volume is used to eliminate internal sensing chamber and reduce lag time, then the response speed is improved, but the ability to isolate scattered light signal from ambient light deteriorates
Solution Approach 1:
The detection system is segmented into multiple independent optical channels: a first optical channel for detecting scattered light from smoke particles and a second optical channel for detecting ambient light. This segmentation allows the system to process signals from different sources separately, enabling the smoke detector to isolate the scattered light signal from ambient light interference while maintaining the external sampling volume configuration that provides fast response speed.
2Device complexity
If external sampling volume is used for flush mounting and aesthetic appearance, then the device complexity is reduced, but the difficulty in distinguishing smoke particles from nuisance particles increases
Solution Approach 1:
Different optical properties are assigned to different detection channels: the first optical channel is optimized for detecting scattered light from smoke particles, while the second optical channel is optimized for detecting ambient light. By assigning different local qualities (optical sensitivity characteristics) to different channels, the system can distinguish between smoke particles and nuisance particles based on their unique light scattering patterns, while maintaining the simple external sampling volume configuration for flush mounting.
3Device complexity
If single wavelength light detection is used to simplify the system, then the device complexity is reduced, but the measurement precision for distinguishing particle types deteriorates
Solution Approach 1:
The system transitions from single-wavelength detection to multi-wavelength detection by introducing a second optical channel with different wavelength sensitivity. This adds a new dimension to the measurement space, allowing the system to distinguish between smoke particles and nuisance particles based on their different light scattering characteristics at different wavelengths. The dual-channel configuration provides sufficient dimensional information for accurate particle type differentiation without excessive system complexity.
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 significantly reduces false alarms and lag time in detecting smoke, enabling more accurate identification of airborne particles and obstructions, thereby enhancing the safety and reliability of smoke detection systems.
Implementation Method 1
one or more light emitters for emitting, outside the housing, light of a first wavelength and a second wavelength longer than the first wavelength
Implementation Method 2
one or more light detectors for detecting light reflected or scattered back into the housing by smoke particles and other objects
Implementation Method 3
detecting light scattered back into the housing by smoke particles located within the sampling volume
Implementation Method 4
detecting light reflected or scattered back into the housing by smoke particles and other objects
Implementation Method 5
an ambient-light sensor to measure and compensate for the ambient light level
Data Source
AI summary
In accordance with certain embodiments, a smoke detector determines the presence of smoke particles outside its housing based on measurements of light detected at different wavelengths and corrected based on an ambient light level.