User Manual

FIREli nk - 25 – Installation Manual Page 17 of 40

9-5-0-344/ISS4/OCT10

Smok e Densi ty hi stogr am Al arm flags

Ther e ar e two types of sm ok e density hist ogr am ; one shown in blue (t he “fast” histogram) whic h updates

ev ery 15 minut es, feeding information to the long-t erm “ slow” histograms (which appear in yell ow). These

set the detector sensitivity based on the am bient smoke condi tions and it takes 24 hours for the two slo w

hist ogr ams (the “day” and the “ night” histograms) t o c om plete their learni ng phase (see sect ion 2.2.6).

Detec tor sensitivity is based on the f ast histogr am during FastLearn and is thereaf ter based on the

curr ently activ e slow histogram. However, alt hough the posi tions of the alarm f lags are based on the slow

hist ogr am , sudden changes in smoke density are pic k ed up by the fast histogram so that earl y warning is

given.

Sensitivity: The c ur r ent absolute sensit ivity of the detector i n per c entage obscuration per metre (%

obs/m)

Mean: The c ur r ent mean value of smoke densit y , taken from the cur r ently “active” histogram and given

as a percentage of full scale deflecti on.

Variance: The “spread” of data in the currently “active” hi stogr am and giv en as a percentage of full scale

deflection.

FastLearn: If the det ec tor is curr ently in FastLear n mode, this will show the number of minutes

remai ning i n the FastLearn period. When this period has elapsed it will read “OFF”.

Alarm factor: This is the ClassiFire alarm factor (see sect ion 3. 5, “Alarm fact or”)

Day/night: This indicates the c ur r ently active sl ow hi stogr am

Alarm levels: These figures give the position of the various alarm flags in terms of a per c entage of full

scale deflection.

Dete ctor output: This shows the real - time variation in bac k gr ound smoke l ev els i n term s of a

percentage of full scale deflection.