ADT Unimode 9600 Installation And Operating Instruction page 125

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 smoothing 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 FACP Status Display
Low Chamber Value
INVREP
Maintenance Alert
DIRTY1
Maintenance Urgent
DIRTY2
Figure 4.1 illustrates a graphic representation of the 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.
Table 4.1 Maintenance Alert Levels
DIRTY
Maintenance
Urgent
Acceptable
Low Chamber
Reading
VALUE
Figure 4.1 Diagram of Maintenance Levels
Maintenance
Alert
Range
LOW