64 AFP-200 Instruction PN 15511:F2 10/11/99
Drift Compensation
Intelligent detector drift compensation provides accurate and stable readings of smoke, counteracting long-term
drift caused by dust contamination and other long term environmental factors. Drift compensation permits a
detector to remain within performance specifications throughout its life span, quickly detecting true fires, yet
rejecting false signals. The drift compensation algorithm uses three measurements from each ionization or
photoelectric detector. Drift compensation can be selected on a per-detector basis (refer to Programming).
• Long-term measurement of location’s clear air. This is an average reading which moves slowly. It adjusts
to gradual buildup of dust contamination, unaffected by true smoke, even from smoldering fires.
• Alarm test level measurement. This uses special electronics in the detector and panel software to periodi-
cally command each detector to simulate an alarm level reading from the sensing chamber.
• Present chamber reading. Under normal conditions, this will be close to the stored air clear value. If smoke
occurs, it will begin to move toward the alarm test level.
The control panel's software converts the present reading to percent per foot obscuration or percent of alarm,
based on its position between the known clean air and test values. The accuracy of this measurement method is
sufficient to meet the NFPA 72E requirements as a calibrated smoke test instrument.
Maintenance Alert
When the compensation reaches the limit of the amount of drift compensation that may safely be applied, a
special trouble condition is reported. This condition will also be activated if the detector remains at very high or
very low levels for extended periods of time.
Automatic Test Operation
The control panel performs an automatic test of each detector every 2 hours. Failure to meet the test limits
causes an AUTO TEST FAIL trouble type. Pressing the System Reset switch clears this trouble.
Type Code Supervision
The control panel monitors hardware device type codes (CPX, SDX, FDX, MMX and CMX) at slow intervals.
Mismatch of type compared to the program will cause a point trouble. The trouble label is INVALID TYPE.
LED Control Operation
The control panel includes a global program selection to prevent blinking of detector LEDs during normal
conditions. This is often desired in sleeping areas where a flashing light may be objectionable. As a standard
function, the control panel allows up to 99 LEDs to turn on in alarm.
Alarm Verification and Counter Operation
The control panel performs Alarm Verification on CPX and SDX intelligent smoke detectors. Selection of
detectors for Alarm Verification is described in the Programming section. Alarm Verification time is a global
programming selection of 0 to 30 seconds. Each detector includes a verification counter which displays the
number of times a detector enters verification but does not time-out to alarm. The counter counts to 99 and
holds.
Pre-Alarm Operation/Advanced Warning Addressable Combustion Sensing (AWACS)
If an SDX or CPX detector exceeds the programmed
Alert level, it causes an Alert Pre-Alarm situation.
When this occurs, the piezo is activated, Zone 99 is
activated, and the Pre-Alarm LED is illuminated. The
typical message displayed to the right is sent to the
LCD, LCD-80, printer and history file.
In the example to the right, the detector is pro-
grammed for alarm at 1.00% per foot of obscuration
(High level), and has now reached the Alert level
programmed for 50% of that, or 0.50% per foot. The 50% is a real-time display and may change. Alert Pre-
Alarms automatically restore.
PREALM@SMOKE(PHOTO)
ROOM@5024
50%,@1.0%,@ALERT
11:13A@12/25/97@D66
4.12 Intelligent Detector Functions, continued
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