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Drift Compensation
Drift compensation uses software algorithms that identify and compensate for long-term changes in
the data readings from each addressable smoke detector. These long-term changes in detector data
readings are typically caused by dirt and dust accumulation inside the smoke chamber. Drift
compensation performs the following functions:
• Allows a smoke detector to retain its original ability to detect actual smoke and resist false
alarms, even as dirt and dust accumulate
• Reduces maintenance requirements by allowing the control panel to automatically perform
the periodic sensitivity measurements required by NFPA Standard 72
The FACP software also provides filters to remove transient noise signals, usually caused by
electrical interference.
Maintenance Alert
The software determines when the drift compensation for a detector reaches an unacceptable level
that can compromise detector performance. When a detector reaches an unacceptable level, the
control panel indicates a maintenance alert. Table 4.1 summarizes the three levels of maintenance
alert:
Maintenance Level
Low Chamber Value
Maintenance Alert
Maintenance Urgent
Figure 4.1 illustrates a graphic representation of the maintenance levels:
FireWarden 100-2/E — P/N 52778:A 11/04/2005
FACP Status Displays
INVREP
DIRTY1
DIRTY2
Table 4.1 Maintenance Alert Levels
DIRTY
Maintenance
Urgent
Acceptable
Low Chamber
Reading
VALUE
Figure 4.1 Diagram of Maintenance Levels
Indicates
A hardware problem in the detector
Dust accumulation that is near but below the
allowed limit. DIRTY 1 indicates the need for
maintenance before the performance of the detector
is compromised
Dust accumulation above the allowed limit.
Maintenance
Alert
Range
LOW
Operating Instructions
147
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