Spectrex 20/20L (LB) - UV/IR Flame Detector - Manual (Page 10)

Spectrex Inc. - SharpEye TM UV/IR Flame Detector Manual – TM20/20LB Rev E, August 2004
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2. Technical Description
• Detection Range: Up to 50 ft (15m) for a 1ft x 1ft (0.3m x 0.3m) Gasoline
fire.
• Ultra High Immunity to False Alarm (see section. 3.3.).
• Advanced Digital Processing of the Dynamic Characteristics of Fire:
Flickering and threshold
• Dual Spectrum: UV and IR radiation
• Multiple Detection Levels: Warning, alarm and saturated signal
• Solar Blind
• Microprocessor Based: Microcontroller performs signal processing
• Built-In-Test: Manual and automatic BIT for 20/20LB only
(see section 4.5)
• Electrical Interface:
o
Dry contact RELAYS.
o
4-20mA outputs.
2.1 Principles Of Operation
The Model 20/20L, 20/20LB Radiation Flame Detector is an electronic device
designed to sense the occurrence of fire and flames and subsequently activate
an alarm or an extinguishing system directly or through a control circuit.
The UV-IR Radiation Flame Detector is a dual spectrum optical detector sensitive
to two separate ranges of the radiation spectrum, both of which are present in
fires. The detector monitors the protected volume, by measuring the radiation
intensity in it, within two frequencies ranges of the electromagnetic spectrum,
namely the Ultra-Violet (UV) and the Infra-Red (IR).
The detector integrates two dependent channels in which appropriate detection
pulses are registered and further analyzed for frequency, intensity and duration.
2.2 Sensing Elements
The IR sensor is sensitive to radiation over the range of 2.5-3.0 micron. The IR
channel will register a detection signal, at the appropriate level, when the IR
sensor is exposed to radiation in the appropriate frequency range, having an
intermittent gleam pattern characteristic to flickering-fire, and a preset threshold
and time duration are reached.
The UV sensor is sensitive to radiation over the range of 0.185-0.260 micron.
The UV channel incorporates a special logic circuit that eliminates false alarms
caused by solar radiation and other non-fire UV sources. Further more; the UV
channel sensitivity is stabilized over the working temperature range.