Led Operation - Bosch 520 Series Operation Manual

8 en | Product Description
The LEDs (refer to Configuration of the Detector, page 7 (3)) transmit light at a defined angle
into the measuring area (refer to Configuration of the Detector, page 7 (7)). In case of fire, the
light is scattered by the smoke particles and strikes the photo diodes (refer to Configuration of
the Detector, page 7 (2)), which transform the quantity of light into a proportional electrical
signal.
The effects of daylight and commercial lighting sources are filtered out with an optical daylight
filter and by the use of electronic filtering and phase-locked rectification (ambient light
stability: dazzling test EN 54‑7).
The various light-emitting and photo diodes of the detector are individually activated.
Consequently, signal combinations are produced that are independent of each other and
ideally suitable for the detection of smoke, which makes it possible to differentiate between
smoke and interference agents (insects, objects). In addition, the time characteristics and the
correlation of the optical sensor signals for the fire or interference detection are evaluated.
Moreover, plausibility checking of the various signals makes it possible to detect errors in the
evaluation electronics and the LEDs.
Chemical sensor (CO gas sensor)
The gas sensor (refer to Configuration of the Detector, page 7 (4), only FAP‑OC 520(-P)) detects
mainly the carbon monoxide (CO) that is produced by a fire, but it also detects hydrogen (H)
and nitrogen monoxide (NO).
The basic measuring principle is CO oxidation on an electrode and the measurable current
that arises from this. The sensor signal value is proportional to the concentration of gas. The
gas sensor supplies additional information in order to reliably suppress the disturbance
variables.
The CO sensor is monitored by supervision of the internal capacity. If the capacity lies outside
the permitted range, a malfunction signal is output on the fire panel. In this case, the detector
continues to operate purely as a scattered light smoke detector.
Pollution sensor
The contamination level of the detector surface is measured and evaluated continuously by the
pollution sensor (refer to Configuration of the Detector, page 7 (6)). A three-stage
contamination display can be read out at service (refer to Maintenance and Service, page 23).
1.5

LED Operation

The two-color LED of the detector indicates the operation and alarm statuses.
During the whole life cycle, the sensors are self-monitored and the sensitivity is self-adjusted
according to the programmed threshold. In case the detector is heavily contaminated, a
message is sent to the fire panel.
In case of an alarm, the LED flashes red. The detector is set back to standby if the alarm is
reset via the fire panel and if the cause of the alarm is gone.
LED Operation
Status
Standby
Alarm
Trouble
Test mode
2019.11 | 4.0 | F.01U.025.877
LED
off
red, flashes
off
green, flashes once every second
Operation Guide
Automatic Detectors LSN improved
Bosch Sicherheitssysteme GmbH