2-32 Operating 15088: J 10/22/99
Section Eight
Drift Compensation
Drift Compensation
AM2020/AFP1010 software is designed to automatically compensate for chamber sensitivity drift due to
detector contamination in SDX-551/751 photo detectors and CPX-551/751 ion detectors. This software-based
compensation meets NFPA 72, Chapter 7 "Inspection, Testing, and Maintenance" periodic sensitivity testing and
maintenance requirements without removing and testing each smoke detector in an installed system. This does
not eliminate the need for visual inspection or testing for smoke entry.
Alarm sensitivity in a detector chamber tends to increase over time. This increase is caused by chamber
contamination. In time, if the clean air level exceeds the alarm threshold a false alarm occurs. Drift
compensation eliminates this problem by increasing the alarm threshold as needed to maintain constant
sensitivity. When the detector is too dirty to compensate, a trouble is indicated automatically.
No additional programming is required for drift compensation. Every detector has three sensitivity levels: low,
medium, and high. These levels assign specific "percent obscuration per foot" values for each device.
Drift compensation is executed when:
• The system powers up.
• A non-communication INVALID REPLY clears.
• Every 120 hours based on at least four samples.
Whenever a detector is replaced, an immediate compensation must be forced. The installer should remove
the existing detector, wait for at least three minutes, and then install the new detector.
After servicing a system containing drift compensation software, some detectors may cause a drift
compensation trouble indication within 15 minutes after reapplication of power. These detectors may have
undergone several drift sensitivity adjustments in the past and may not be properly compensated during power
up compensation. A second compensation may be required before the trouble condition clears. This second
compensation will be completed automatically after 120 hours. If a trouble condition for a detector still exists
after a second compensation, clean and/or replace it.
If power has not been removed and reapplied recently and drift compensation trouble is indicated for a
particular device, clean and/or replace the detector immediately.
ytivitisneSwoL
)toofrepnoitarucsbo%(
ytivitisneSmuideM
)toofrepnoitarucsbo%(
ytivitisneShgiH
)toofrepnoitarucsbo%(
rotceteDotohP 0.25.10.1
rotceteDnoI 0.35.10.1
www.PDF-Zoo.com
To Next Page
Loading...
Need help?
General
