Spectrex 40/40L-LB UV/IR Flame Detector Series - Manual (Page 17)

TM 40/40L, Rev (6) February 2013
Principles of Operation 5
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 frequency 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.
 Sensing Elements
The IR sensor in Models 40/40L and LB is sensitive to radiation over the
range of 2.5-3.0 micron where the H
2
emission has a unique spectral
peak that enables detection of hydrocarbon fires, gas fires, hydroxyl and
hydrogen fires as well as metal and inorganic fires.
The IR sensor in models 40/40L4 and L4B is sensitive over a range of
4.4-4.6 µm spectral band where the CO
2
has a unique spectral peak that
enables it to detect the combustion product of any organic substance.
The UV sensor is sensitive to radiation over the range of 0.185-0.260
µm. The UV Channel incorporates a special logic circuit that eliminates
false alarms caused by solar radiation and other non-fire UV source.
Furthermore, the UV channel’s sensitivity is stabilized over the working
temperature range.
 Detection Levels
Simultaneous detection of radiation in both the UV and the IR channels
having an intensity that exceeds the detector’s preset Warning level
results in a Warning signal.
Simultaneous detection of radiation in both the UV and the IR channels
having an intensity that exceeds the detector’s preset Alarm level results
in an Alarm signal.
Simultaneous detection of radiation in both the UV and the IR channels
having an intensity that exceeds the detector’s preset Flash-Fire
Detection level results in an immediate Alarm signal.
Since the preset dual range and level of radiation, as well as the flickering
pattern, are characteristics of real fire, all other radiation sources apart from
actual fire are not detected, thus avoiding false alarms.
1.4.2 Heated Optics
The SharpEye 40/40 Flame Detectors use heated optics. The heater
increases the temperature of the optical surface by 5-8°F (~3-5°C) above
the ambient temperature to improve performance in icing, condensation and
snow conditions.
The heated optics can be set to one of the following:
 Not operated
 On continuously