VESDA -E VES-A00-P Product Manual page 71

5.5.10 Referencing Options
Periodically, smoke and other pollutants from external sources may enter a protected zone temporarily raising
the smoke level. In this case the detector will detect the background smoke and generate an alarm.
Referencing is a system design technique employed to compensate for such rises in background smoke
levels and therefore reduce nuisance alarms in high sensitivity areas.
A separate non-scanning VESDAnet-capable detector is used to draw air from the external source and
produce a reference reading of the background level of smoke and pollutants. The reference reading is then
subtracted from the smoke level of the VES-A00-P detector monitoring the protected area. This allows the
VES-A00-P detector to determine if a rise in smoke levels is due to background pollution or a problem inside
the protected area. The ability to compensate for the background level of smoke greatly reduces the chance of
false alarms.
The smoke level from the reference detector which is subtracted from the smoke level of the VES-A00-P
detector monitoring the protected area is limited to 50% of the Fire 1 alarm threshold of the VES-A00-P.
A single reference detector can be used by multiple VESDA detectors within the protected area.
The percentage of reference smoke level subtracted can be set differently for each detector monitoring the
protected area. This is set using the dilution factor parameter.
There may be a time delay before the smoke moves from the external source to the protected area. This delay
can be accounted for by delaying the measured reference smoke level before subtracting it from the VES-A00-
P detector smoke level. This is set using the delay parameter..
Note: Refer to Section 5.6 on page 71 for the default settings.
The Referencing configuration options are as follows:
Referencing Enabled: If checked, referencing is enabled.
l
Detector: The name of the detector or system which provides the reference signal. Select from other
l
non-scanning detectors on the VESDAnet.
Delay: The length of time between the measurement of the external smoke level by the reference
l
detector and the internal subtraction of this smoke level from the VES-A00-P smoke level.
Dilution Factor: The percentage of the reference signal to be subtracted from the VES-A00-P.
l
www.xtralis.com
Figure 5-21: Referencing Options
VESDA-E VES-A00-P Product Guide
65