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1

Flame Detection Design: A Balancing Act

DetectionCapability

• Range • Fuel

InterferenceRejection

• Resistance level• Impact on Flame

Detection

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2

Flame Detection

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3

Solar radiation

Wavelength (microns)

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4

Typical interference

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5

UV detectors

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6

Ultraviolet Sensor Operating Principle

• Solar blind 1850 to 2450 • UV photons strike tube cathode• Cathode releases electron• Electron strikes gas molecule• Cascade effect occurs to anode• Discharge is quenched, creates pulse

(count) output• Pulse output measured in CPS

(counts per second)

Anode

CathodeOi Test Source

Plastic housing

connectors (a,b,c,d)

Quartz Envelope

Det-Tronics UV Sensor

circuit board

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7

• Enhanced Arc Rejection• Faster and more false alarm

resistant

Ultraviolet Flame Detector

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8

IR detectors

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9

IR Sensor Operating Principle

• Optical filter mounted to sensor• 4.45 micron band-pass• Flicker modulation required• Steady state IR sources ignored

Optical Bandpass

Filter

Pyroelectric Infrared Sensor

Infrared Energy

Flicker Filter

Circuitry

Output Circuitry

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• Analyzes the raw IR sensor signal “randomness”• Rejects signals that do not meet randomness criteria

No Fire Alarm

Fire Alarm!

TDSA

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Single Frequency Infrared Flame Detector

• TDSA IR signal processing• Quick fire response• Heated optic

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12

UV/IR detectors

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• ARC UV and TDSA IR signal processing• High Speed• Heated IR optic sensor

Ultraviolet Infrared Flame Detector

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14

Ultraviolet Infrared Signal Processing

• Dual Spectral Processing– Arc rejection UV sensor– TDSA IR sensor

• UV sensor (and gated) with the IR sensor• Alarm only when processing time is met by both sensors

simultaneously

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15

Multi-spectrum IR detector

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Spectral Analysis

• Determine unique spectral features of sources

• Use multiple Infrared bandwidths to optimize desired

capabilities

• Develop algorithms to identify signatures

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Typical signal/reference band multi IR

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• Patents– Wavelength– Algorithm– Digital signal Processing

• Extended Cone of Vision

X33AF Multispectrum Infrared Flame Detector

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X33AF IR3X33AF Multi-spectrum63m‘

UV/IR

UV/IR 30m

SFIR

SFIR 25m

COV Test data for 1’ * 1’ gasoline fire