Det-Tronics C7050 A, C, G, P UV Flame Detector - Manual (Page 5)

The output of the detector consists of a series of voltage
pulses or “counts.” The frequency of these pulses is
directly proportional to the intensity of the radiation being
detected and is measured in counts per second (cps).
oi
The detector is equipped with the Automatic oi feature
(Figure 1). A UV test lamp is mounted in the same
enclosure with the UV sensor tube, but they are optically
isolated from each other by a cylindrical shield. When
the test lamp is actuated by a signal from the controller,
it generates a UV test signal that travels out through the
viewing window, where it encounters the reflective
oi
ring and is directed back through the window to the sen-
sor. The controller evaluates the strength of the return
signal to determine the relative condition of the detector
and its optical surfaces. Since this UV test signal must
pass through the same portion of the viewing window as
UV radiation generated by a flame, a reliable test of the
ability of the detector to “see” a fire is achieved.
The controller continuously executes the automatic oi
test, sequentially testing each detector connected to it.
If a fault should occur in the system, it is quickly detect-
ed and registered on the digital display on the front
panel of the controller and the Fault output is de-ener-
gized.
Internal Reflection oi
The use of an Internal Reflection oi detector is recom-
mended in applications where corrosive or oily contami-
nants are present in the atmosphere. This type of envi-
ronment can cause rapid deterioration of the reflectivity
of externally mounted
oi rings, resulting in the need for
frequent detector maintenance. Since the Internal
Reflection detector checks the cleanliness of the viewing
window without the use of an external reflective
oi ring,
faults caused by corrosion or contamination of the ring
are eliminated. A fault will be indicated only if the view-
ing window is actually dirty. It is important to note that
the internal reflection system is effective only with oily
substances that wet the surface of the window. It does
not detect dry contaminants and, therefore, is not practi-
cal for powder coating booths or similar applications
where various dry contaminants can obscure the vision
of the detector.
UV detectors that are currently using the external reflec-
tion
oi system can easily be converted to Internal
Reflection in the field by simply replacing the existing
sensor tube module with a DE1888V Internal Reflection
oi Tube Module. No calibration or other adjustments are
required, and no modifications to the detector enclosure
are needed.
Detector Enclosure
The detector is housed in an explosion-proof enclosure
that is designed to meet most national and international
standards. It is available in various materials to meet the
requirements of the environment in which it is used.
Materials include anodized aluminum, nickel-plated
brass and 316 stainless steel. The aluminum and the
nickel-plated brass housings are epoxy coated, making
them suitable for use in high saline atmospheres, such
as offshore platforms.
The detector is typically mounted on an optional swivel
mounting assembly (Model Q9001), which is recom-
mended for ease in installation. Other mounting
arrangements are also available, such as a quick-
connect front mount for applications involving paint
spray or powder coating booths, or for looking inside
mixers, kettles, conveyors and other inaccessible areas.
CONTROLLER
The R7404 is designed for use with 24 volt dc power
supplies, but will operate from any direct current supply
between 10 and 38 volts. The unit will tolerate transients
such as those that can occur when fully discharged bat-
teries are placed on charge. When power is present at
the R7404 Controller, it is indicated by a continuously
energized green LED. All other lights and displays on
the R7404 panel are normally off, but may be periodical-
ly checked for operation by pressing the LAMP TEST
button located directly opposite the POWER light as
illustrated in Figure 2. It is not necessary for the con-
troller to be in the TEST mode when this check is per-
formed.
The R7404 Controller incorporates a microprocessor and
a programmable-read-only-memory (PROM) to store and
implement the permanent program for operating the sys-
UV DETECTOR
UV TEST LAMP
OPTICAL SHIELD
VIEWING WINDOW
SNAP-IN oi RING
UV SENSOR
C784
Figure 1—Detector with oi
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