Operating Instructions—IFC-200 Operating Instructions 11
The system can be programmed to automatically force smoke detectors to
their minimum sensitivity (3.0%) during the day. For more information,
refer to the information on Time Control Command Operation later in this
chapter.
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. It permits a
detector to remain within performance specifications throughout its life
span, quickly detecting true fires while rejecting false signals. The drift
compensation algorithm uses three measurements (described below) from
each ionization or photoelectric detector. Drift compensation can be
selected on a per detector basis. Refer to the IFC-200 Programming/
Status Change Technical Bulletin in this manual for further information.
Drift compensation provides a long-term measurement of a location’s
clear air. This is an average reading that moves slowly. It adjusts to a
gradual buildup of dust contamination, unaffected by true smoke, even
from smoldering fires.
Drift compensation also provides alarm test level measurement. Special
electronics in the detector and panel software periodically command each
detector to stimulate an alarm level reading from the sensing chamber.
Under normal conditions, present chamber readings are close to the
stored air clear value. If smoke occurs, the chamber reading moves toward
the alarm test level.
IFC-200 software converts the present chamber reading to percent per foot
(%/ft) obscuration, based on its position between the known clear air and
test values. The accuracy of this measurement method meets NFPA 72E
requirements for calibrated smoke test instruments.
Upon reaching the limit of drift compensation that may be safely applied,
a trouble condition is reported, per NFPA standards. This trouble
condition also activates if the detector remains at very high or very low
levels for an extended period of time. Below is a typical LCD display
when a trouble condition is reported.
TROUBL PULL STATION
WEST HALLWAY FLR 5
Z05 OPEN CIRCUIT
11:13A 12/25/94 M37
Day/Night
Sensitivity
Operation
Drift
Compensation
Maintenance
Alert
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