Open Scattered Light Smoke Detector Phase Angle Service Mode
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Solution Overview
Problem
Open scattered light smoke detectors face challenges in accurately distinguishing between changes in optical path length and potential smoke presence, leading to false alarms and operational inefficiencies, particularly when the detection space exceeds a certain distance from the detector.
Innovation Solution
The implementation of a control unit that switches the smoke detector into a service mode based on a sudden increase in phase angle between emitted and received signal sequences, allowing for suppression of false alarms and enabling testing and data encoding for internal detector data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the detection space is positioned at a greater distance from the detector, then the detection coverage area is improved, but the phase angle measurement accuracy deteriorates leading to false alarms
Solution Approach 1:
The system dynamically adjusts the evaluation criteria for smoke detection based on the measured phase angle. When the phase angle indicates a large optical path length (greater than 6m or 10m), the system modifies its evaluation parameters to account for the increased distance, thereby maintaining measurement accuracy and preventing false alarms while preserving extended detection coverage.
2Use of energy by moving object
If the light transmitter is actuated repeatedly with pulsed signal sequences, then the energy consumption is reduced, but the complexity of signal evaluation increases
Solution Approach 1:
The control unit implements feedback mechanisms that monitor the phase angle between emitted and received signal sequences. This feedback information is used to adjust evaluation parameters and distinguish between legitimate smoke detections and false alarms caused by large optical path lengths, thereby managing signal evaluation complexity while maintaining pulsed operation energy efficiency.
3Length of stationary object
If the phase angle threshold is set to detect smoke at larger distances, then the detection range is improved, but the false alarm rate increases
Solution Approach 1:
The system dynamically modifies evaluation parameters based on the measured phase angle. When the phase angle exceeds certain thresholds (indicating optical path lengths greater than 6m or 10m), the system adjusts its detection criteria to account for the increased distance, thereby maintaining an extended detection range while suppressing false alarms through parameter adaptation.
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 solution effectively reduces false alarms by selectively deactivating the alarm during harmless events and allows for efficient testing and data transmission, enhancing the operational reliability and usability of the smoke detector.
Implementation Method 1
open scattered light smoke detectors... light transmitter for emitting light... and a light receiver which is spectrally matched to this
Implementation Method 2
the control unit is configured to switch the scattered light smoke detector from a normal operating mode into a service mode if a phase angle, determined on the detector side, between an emitted and a received signal sequence increases
Data Source
AI summary
An open scattered light smoke detector for detecting smoke may include a light transmitter for emitting light, a light receiver spectrally matched to the light transmitter, and a control unit configured to repeatedly actuate the light transmitter, with a pulsed signal sequence, to emit corresponding light pulses, evaluate temporally a signal sequence received by the light receiver, and output a fire alarm if a received signal strength exceeds a minimum value for the smoke concentration. The control unit may be configured to switch the detector from a normal operating mode into a service mode if a phase angle between an emitted and received signal sequence, as determined on the detector side, increases by a minimum angular value which, in terms of the travel time, corresponds technically to an increase in the optical path length from the light transmitter to the light receiver of more than some predefined distance.