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3
DISCOVERY FEATURES –
SMOKE AND HEAT DETECTORS
Response setting
Each detector in the Discovery range can
operate in one of five response modes, any of
which can be selected from the control panel.
Each mode corresponds to a unique response
behaviour, which can be broadly related to
sensitivity to fire. Whatever the type of
detector, Mode 1 will give a higher sensitivity
to fire than Mode 5. The selection of the most
suitable mode depends on the application.
Guidance on detector and mode selection is
given on pages 21-23.
For ionisation and optical smoke detectors,
the modes relate to different combinations of
smoke response threshold and response time.
For the heat detector, the mode relates to the
fixed temperature setting and the sensitivity to
rate-of-rise of temperature. For the
multisensor, the mode relates to the levels of
smoke and heat sensitivity and to the way in
which the responses of the two sensors are
combined.
The response characteristics of the detectors
have been carefully set so that detectors will
comply with the requirements of the relevant
part of EN54 in all response modes. The
mathematical algorithms embedded in the
detectors are used to carry out changes in
characteristics between modes. Since the
response characteristics are defined within
the detectors, Apollo takes responsibility for
compliance with standards in different response
modes.
The internal signal processing of the detectors
is designed so that the analogue value
reported is always close to 25 for a normal
condition. The alarm threshold is 55,
irrespective of the response mode selected.
Similarly, the alarm flag in the protocol is
always set when the analogue value exceeds
55, irrespective of mode. This simplifies the
switching between response modes since the
alarm threshold in the control panel can
remain fixed at 55 and the alarm flag is valid
in all modes.
The response mode, which is selected
through the protocol, is stored in non-volatile
memory and will therefore be retained when
the detector is powered down. All Discovery
detectors are factory set to mode 3 before
shipping.
Response modes are defined more fully in the
individual detector descriptions.
User bytes and other stored data
All Discovery devices contain non-volatile
memory, in the form of Electrically Erasable
Programmable Read Only Memory
(EEPROM), which is included primarily to
store data needed for the correct operation of
the device. However, four bytes of this
EEPROM are available to the user and can be
accessed by the control panel through the
protocol. This block of non-volatile memory
can be used, for example, to store the
installation date, the site code or date of last
service. The only restriction on use is that the
maximum number of write cycles should not
exceed 20,000 over the life of the device.
The way in which this memory can be
accessed is described in the Discovery
Protocol PIN Sheet PP2027.
(11 paginas)
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