TM 40/40M, Rev (14) February 2017
Principles of Operation
17
1.4.1 Fire Detection Principle
The SharpEye 40/40M Detector is designed to detect hydrocarbon flames
that produce CO
2
in their combustion process and non-hydrocarbon flames
that produce mainly water vapor (H
2
O) from inorganic fuels, for example,
hydrogen, ammonia, hydrofluoric acid, hydrochloric acid and so on.
The detector's principle of operation is based on the patented spectral
analysis technology that identifies the IR spectral signature of fire products,
i.e. the hot CO
2
spectral emission band at wavelengths of 4.2
–
4.7µm and
the hot water (H
2
O) spectral emission band at wavelengths of 2.7
–
3.0µm.
Additional spectral bands (above and below these bands) are analyzed for
background interferences.
The spectral analysis incorporates several detection algorithms, according to
several types of fire events, taking into account simultaneous detection of
both CO
2
and H
2
O peaks, or only one of them, as well as flickering analysis
at frequencies typical to these flames. Only when all the parameters of the
spectral analysis and the flickering analysis meet the predetermined values,
is a fire condition identified and the fire alarm is issued.
When exposed to non-fire radiation sources, these parameters do not
identify a fire condition and the detector does not react.
1.4.2 Heated Optics
The SharpEye 40/40 Flame Detector uses 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 ice, condensation, and
snow conditions.
The heated optics can be set to one of the following:
Not operated.
On continuously.
Automatic, per temperature change (default): you can define the start
temperature below which the window is heated. (The default is
41°F/5°C.) This temperature can be defined from 32°F/0°C to
86°F/30°C. The heating stops when the temperature is 27°F/15°C above
the start temperature.
on page 45.
1.4.3 HART Protocol
The SharpEye 40/40 Flame Detectors use the HART protocol.
HART Communication is a bi-directional industrial field communication
protocol used to communicate between intelligent field instruments and host
systems. HART is the global standard for smart process instrumentation and
the majority of smart field devices installed in plants worldwide are HART-
enabled. HART is available in wiring options 1, 2, and 3 (see
HART technology is easy to use and very reliable.
