Document No: LT0117 F4000 LCD Operator's Manual
Operating Instructions - Point Functions
Issue 2.38 19 April 2002 Page 8-9
OPERATING SEQUENCE - SPECIFIC POINT DETECTOR DIRTY LEVEL (CONT’D)
To view the % Dirty levels of other points, press:
to view the % Dirty level for the next configured point.
to view the % Dirty level for the previous configured point.
NOTES: One measure of the useful life of a detector is how far its Tracked Value (TV) has
shifted from its “as manufactured” clean air value “Clean Air Max” towards the
Upper Tracking Limit (UTL). UTL, combined with the detector’s Alarm Sensitivity
“AS”, determines the maximum TV at which the detector’s sensitivity is
unaffected. The increase in TV over time is usually a result of contamination.
The % Dirty level of a detector is then determined by calculating how far between
Clean Air Max and UTL-AS the TV is.
Searching for detectors that are more than, say 80% dirty, allows for
maintenance of those detectors before they start becoming more sensitive,
and/or Dirty Alert is signalled for that detector.