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Laser Dust Discrimination

Laser Dust Discrimination

Stratos series aspirating smoke detectors use a revolutionary dust discrimination algorithm known as LDD-3D3™ which make the system suitable for dusty and challenging environments reducing or eliminating the occurrence of nuisance alarms.
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How it works
The system works on the principle that the laser sensor signal will show a steady output (caused by the homogeneous distribution of smoke particles throughout the moving air sample), with ‘spikes’ caused by any dust particles intermittently passing through the point of laser focus on the moving airstream. Any dust present will cause these ‘spikes’ to be superimposed on the smoke reading signal. LDD-3D3™ works on the principle that if these spikes can be eliminated from the underlying detector signal, then the steady output which remains would represent the underlying smoke density present. The result is greatly enhanced dust rejection by these detection products.
  
  • The average signal (arithmetic mean) of the 50 readings is calculated. All readings above the average are removed.
  • A second average (arithmetic mean) is calculated using all the remaining readings (those below or equal to the previously calculated average).
  • The second average is considered to be the detector output for the cycle. It is passed to a selectable moving average arithmetic routine to reduce slower variations in chamber output.
  • The result of the moving average is compared to the alarm thresholds to establish if a fire condition exists and passed to ClassiFire® to be added to the histogram.