Spectrex 20/20MI - Mini Triple IR (IR3) Flame Detector - Manual (Page 11)

Spectrex Inc. - SharpEye TM Mini IR3 Flame Detector Manual – TM 787100, Rev. D April 2011
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2. Technical Description
• Detection Range: up to 132 ft (40m) for a 1 ft
2
(0.1m
2
) fire.
• Ultra High Immunity to False Alarms (see section. 3.3).
• Advanced Digital Processing of the Dynamic Characteristics of Fire:
Flickering, Threshold correlation and Ratio.
• Three Separate IR Channels: Between 3-5 microns.
• Field Programmable Sensitivity: four ranges.
• Two Response Levels: Warning & Detection.
• Solar Blind
• Microprocessor Based: Digital signal processing.
• Built In Test (BIT): Manual and Automatic (see section. 4.4).
• Electrical Interface:
o Dry contact relays (non-Ex version).
o Communication network RS-485.
o 4-20mA output.
• Certification: ATEX (Cenelec)
2.1 Principles Of Operation
2.1.1 Hydrocarbon fire detection
The triple IR flame detector detects all conceivable types of hydrocarbon fires, i.e.
any fire, which emits CO
2
.
2.1.2 Identifying the CO
2
peak
The hydrocarbon fire is characterized by a typical radiation emission. The CO
2
peak emits intense radiation in the spectral band between 4.2 µ - 4.5 µ and
weaker radiation intensity outside this spectral band.
2.1.3 The limitations of IR-IR flame detectors
CO
2
in the atmosphere attenuates the radiation in this spectral band. (Absorption
and emission of radiation always occur in the same band.) As a result, the greater
the distance between the detector and the fire, the weaker the intensity of the
radiation reaching the detector (the CO
2
attenuation increases). This phenomenon
explains the limitations of the existing IR-IR flame detectors in the market:
• Detection distance is restricted to 33ft (10 m) only.
• Their immunity to false alarm sources is limited.
2.1.4 The advantages of IR3 technology
To overcome these limitations, Spectrex Inc. devised an innovative concept of
utilizing an additional detection channel. Three channels collect more data from
the environment, permitting more accurate analysis and better performance.