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172 MS-9600LS Series Manual — P/N 52646:B2 2/12/2010
Operating Instructions Read Status
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 com-
pensation performs the following functions:
• Samples each photoelectric smoke detector every 6 seconds and each ionization smoke
detector every 3 seconds
• 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 elec-
trical 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:
Figure 4.1 illustrates a graphic representation of the maintenance levels:
Maintenance Level FACP Status Displays Indicates
Low Chamber Value
INVREP
A hardware problem in the detector
Maintenance Alert
DIRTY1
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
Maintenance Urgent
DIRTY2
Dust accumulation above the allowed limit.
Table 4.1 Maintenance Alert Levels
Figure 4.1 Diagram of Maintenance Levels
DIRTY
Acceptable
Range
Maintenance
Urgent
Maintenance
Alert
Low Chamber
Reading
LOW
VALUE