Apollo Smoke Detector XP95 Betriebsanweisung PDF herunterladen (Seite 7)

DISCOVERY FEATURES –

SMOKE DETECTORS

Drift compensation

All Discovery smoke detectors include

compensation for sensor drift as part of the

internal signal-processing algorithm. The

algorithm will compensate for changes in

sensor output caused, for example, by dust in

the chamber, and will therefore hold the

sensitivity at a constant level even with

severe chamber contamination. This

increased stability is achieved without

significantly affecting the detector’s

sensitivity to fire.

The compensation level is stored in the

detector’s memory as a single value between

0 and 31. The normal level, that is, with no

compensation applied, is 16. Values above

or below this indicate drift towards alarm or

away from alarm respectively.

For compensation values in the range 4 to 30

the detector is working within its allowable

range. A value which is less than 4 or greater

than 30 results in a warning flag. A value of

zero results in a fault signal.

The maximum compensation that can be

applied is 31. If further drift occurs, the

analogue values will simply track the drift

and the detector will become more sensitive.

Compensation values are stored in non-

volatile memory and will be retained even if

detectors are disconnected. It is possible to

use the control panel to ascertain the level of

compensation applied at any time.

For the Discovery smoke detectors, the

compensation algorithms are designed such

that the detectors meet the requirements of

the European draft standard EN54

–

7:2000 in

all response modes.

It is possible, through the protocol, to carry

out a normalisation procedure which rapidly

“updates” the drift compensation. This

facility may be useful during commissioning

when detectors can be quickly acclimatised

to the prevailing ambient conditions, or after

a compensated detector has been cleaned.

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5

Fig.1 Drift Compensation Graph

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