System Overview; Functional Description Of The Sensor Technology; Optical Sensor (Smoke Detector); Thermal Sensor (Heat Detector) - Bosch AVENAR 4000 FAP-425-O User Manual

AVENAR detector 4000
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System Overview

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Figure 2.1: Detector set-up
1 Smoke measurement chamber with
2 Thermal sensor
3 Chemical sensor (covered on the cross-
2.1

Functional Description of the Sensor Technology

2.1.1

Optical Sensor (Smoke Detector)

This optical sensor utilizes the scattered-light method.
An LED sends light into the measuring chamber, where it is absorbed by the labyrinth
structure. In the event of a fire, smoke enters the measuring chamber. The light is scattered by
the smoke particles and hits the photo diodes, which transform the quantity of light into a
proportional electrical signal.
The DO detectors have a dual optical sensor that uses the different infrared and blue light
wavelengths (Dual Ray technology). This allows fires to be detected early and even the
smallest quantities of smoke (TF1, TF9) to be reliably detected.
Notice!
The FAP-425-DO-R, FAP-425-DOT-R and FAP-425-DOTC-R smoke detectors make an alarm
i
decision based on an intelligent combination of the following criteria:
Amount of smoke density measured
Speed of smoke density increase
Size of smoke particles (as measured by Dual Ray technology)
2.1.2

Thermal Sensor (Heat Detector)

A thermistor in a resistance network is used as a thermal sensor; an analog-digital converter
measures the temperature-dependent voltage at regular intervals.
Depending on the specified detector class, the thermal sensor triggers the alarm status when
the maximum temperature of 54 °C or 69 °C is exceeded (thermal maximum), or if the
temperature rises by a defined amount within a specified time (thermal differential).
Bosch Sicherheitssysteme GmbH
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5
optical sensor
section)
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4 Individual display
5 PC board with evaluation electronics
6 Detector Base
User manual
System Overview | en 5
2021-11 | 4 | F.01U.283.550