System Overview; Detector Configuration; Functional Description Of The Sensor Technology; Optical Sensor (Smoke Detector) - Bosch FAP-DO420 Operation Manual

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System Overview

2.1

Detector Configuration

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2.2

Functional Description of the Sensor Technology

2.2.1

Optical Sensor (Smoke Detector)

This optical sensor utilizes the scattered-light method.
An LED sends light into the measuring chamber (see Figure 2.1, item 1), 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) to be reliably detected.
NOTICE! The FAP-DO420 smoke detector makes an alarm decision based on an intelligent
combination of the following criteria:
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2.2.2

Thermal Sensor (Heat Detector)

A thermistor (see Figure 2.1, item 2) 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).
F.01U.003.448 | 8.0 | 2011.10
Smoke measurement chamber with
optical sensor
Thermal sensor
Chemical sensor (covered on the cross-
section)
Individual display
PC board with evaluation electronics
MS 400 / MS 400 B Detector Base
Amount of smoke density measured
Speed of of smoke density increase
Size of smoke particles (as measured by Dual Ray Technology)
Operation Guide
Automatic Fire Detectors LSN improved
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Figure 2.1 Detector Configuration
Bosch Sicherheitssysteme GmbH
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