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The six alarm algorithms for the detectors 430x and 440x in NORMAL mode. Default is
alarm algorithm N-15, i.e. normal detection time (15 sec.) and normal sensitivity (3%).
X=The step value.
X refers to the step value.
Note: the L-15, H35, N-35 and L-35 algorithms may not comply with the AS7240.7
requirements.
Figure 37 Filtering algorithm example for analogue smoke detector
Figure 37 shows an example of the filtering algorithm for an Analogue smoke detector with
the step value X = 5. The polling time (t) in this example is approx. 2.56 seconds.
Explanations to the Figure 37:
In this example, the week average sensor value is "10" (=1.0%/m) at the "starting point",
i.e. due to contamination, the pre-warning level has been adjusted to "32" (10+22) and the
fire alarm level to "40" (10+30). The sensor value is accordingly "10".
In this example, alarm algorithm "N-15" is selected, i.e. normal detection time 15 sec. and
normal sensitivity 3% (30). X = 5. The detector polling time t ≈ 2.56 sec. (In system
FT1020G3 the detector polling time t ≈ 7 seconds and the step value "X" is according to
Figure 37– but the principle is the same.)
The sensor values and decision values at start are approx. equal ("10"). When smoke
enters the detector, the sensor values are increasing and by the fourth polling approx. "27".
Since 27-10 > X=5, the decision value ("10") is increased by X=5 to "15". Next polling the
sensor value is approx. "45", i.e. the decision value ("15") is increased by X=5 to "20", and
so on. In this example the decision value never reach to the fire alarm level. When the
sensor value is reduced to approx. "25" the decision value is set to "30", because 35-25=10
> X=5, i.e. the decision value ("35") is reduced by X=5 to "30", and so on.
Refer to Figure 37, these comments refer to the numbered points on the graph:
1.
The sensor value has here reached the pre-warning level but nothing will happen
since the decision value has not reached the pre-warning level.
2.
The sensor value has here reached the fire alarm level but nothing will happen
since the decision value has not reached the fire alarm level.
Technical/Programming Manual
105
FT1020G3 Rev 2.2.1
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