Det-Tronics C7052J UV/IR Flame Detector used with R7494, R7495 Controller - Manual (Page 18)

Rocker switch assemblies 2 and 3 control three vari-
ables; gate length, counts per gate and consecutive
gates required for a fire output. Refer to Figure 21 for a
visual representation of how these variables function
together with typical controller settings. Keep in mind
that when the UV and IR sensors of the detector
respond to a fire, the IR sensor activates the circuitry in
the UV/IR detector junction box. This allows the electri-
cal pulses (signal) from the UV sensor to be sent to the
controller. The frequency of this signal is proportional to
the intensity of the fire. The controller looks at this sig-
nal in comparison to the sensitivity settings in order to
determine whether a fire exists. A brief description of
each variable follows:
1. Gate Length is adjustable from 31.25 milliseconds
to 8 seconds. The gate length is the increment of
time that the controller looks at the detector signal
to determine if the “Counts per Gate” requirement is
fulfilled. In Figure 21, the gate length is 0.25 sec-
onds (Rocker Switch 2-4 closed, Rocker Switches
2-1, 2-2, 2-3, 2-5, 2-6, 2-7, and 2-8 open).
2. Counts per Gate is adjustable from 2 to 15 counts.
These counts make up the signal from the detector
and are a direct response to a flame or other UV/IR
source. In Figure 21, the counts per gate setting is
4 counts (Rocker Switch 3-3 closed, Rocker
Switches 3-1, 3-2, and 3-4 open).
3. Consecutive Gates required for a fire output are
adjustable from 2 to 15 gates. This is the number of
consecutive gates in which the “Counts per Gate”
requirement is fulfilled that the controller must see
before going into a fire alarm condition. In Figure
21, the consecutive gates setting is 4 gates (Rocker
Switch 3-7 closed, Rocker Switches 3-5, 3-6, and 3-
8 open).
If changes in the sensitivity and/or time delay settings
are required, read the detailed discussions of each of
the three STAR Logic variables that follows before mak-
ing changes. When changing the settings, keep in
mind the following guidelines:
1. Increasing Gate Length while the other variables
remain unchanged results in higher sensitivity and a
longer time delay.
2. Increasing Consecutive Gates while the other vari-
ables remain unchanged results in a longer time
delay and greater noise immunity.
3. Increasing Counts per Gate while the other vari-
ables remain unchanged results in lower sensitivity
and greater false alarm rejection.
Gate Length - Rocker Switches 2-1 to 2-8
The gate length can be adjusted in 31.25 millisecond
increments from 31.25 milliseconds to 8 seconds. Each
rocker selects a particular time value. The gate length
is the value of all rockers closed, added together. If no
rocker is closed, the controller will select the minimum
length (31.25 milliseconds). The typical gate length set-
tings used in most applications are between 0.125 and
0.5 second.
Rocker 2-1 - 31.25 milliseconds
Rocker 2-2 - 62.5 milliseconds
Rocker 2-3 - 0.125 second
Rocker 2-4 - 0.25 second
Rocker 2-5 - 0.5 seconds
Rocker 2-6 - 1 seconds
Rocker 2-7 - 2 seconds
Rocker 2-8 - 4 seconds
The value of the closed switches are added together to
obtain the total time delay.
Count Selection - Rocker Switches 3-1 to 3-4
When a gate length of less than 0.5 second, the rockers
select counts needed per gate for a fire signal. The val-
ues of all rockers closed are added together. If no
counts or less than 2 counts are selected (only rocker 1
closed), the microprocessor will select 2. Counts per
gate are selectable in 1 count increments from 2 to 15
counts. The typical counts per gate setting used in
most applications are between 2 and 8 counts.
Rocker 3-1 - 1 count
Rocker 3-2 - 2 counts
Rocker 3-3 - 4 counts
Rocker 3-4 - 8 counts
When a gate length of 0.5 second or greater is used, the
programmed counts per gate value is multiplied by a fac-
tor that is determined by the gate length that has been
programmed using rocker switches 2-5 to 2-8. Refer to
Figure 22 to determine the proper multiplication factor.
Note that the multiplication factor is determined by the
highest numbered rocker switch in the closed position.
The STAR logic program uses this multiplication tech-
nique to prevent accidental programming of a very low
count value combined with a long gate length, since this
combination would result in an extremely high sensitivity
level that would increase susceptibility to false alarms.
For example, suppose that a gate length of 1.5 seconds
and a sensitivity of 4 counts per gate is selected. Since
the gate length exceeds 0.5 second, the counts per
gate value must be multiplied by the factor determined
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