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5.3. Indication of normal operation
When the covers of the receiver or emitter are closed then the green LED visible through
the outside of the case will flash every 3 seconds to indicate that the detector is operating
correctly.
If the cover of the receiver is open then both green LED's (the centre alignment LED is not
visible unless the cover is open) on the receiver will flash every 3 seconds. If the cover of
the emitter is open then both green LED's (the centre alignment LED is not visible unless
the cover is open) on the emitter will flash every 3 seconds. The rate of flash will not be
affected by opening the cover of the detector.
5.4. Sensitivity and operation setting
The receiver is provided with a DIP switch with 4 bits available for setting the sensitivity
and operation of the beam detector.
Bits 1 and 2 are allocated to sensitivity setting, while
bits 3 and 4 are allocated to settings by operation type. The sensitivity settings can be
25%; 50%; 70% or no operation. For operation types, bit 3 can be set to switch the
signals to be emitted when the beam is blocked to fault and fire, or to fault alone. Bit 4
can be set to switch between the automatic or manual recovery from the fault status. For
details, see Chapter 2.6.2.
The sensitivity setting only affects the determination of the fire signal. Basically the higher
the percentage setting, the less sensitive the beam detector will be since the production of
a fire signal requires that the signal seen by the receiver should be reduced by more than
the amount of the sensitivity setting. For example a sensitivity of 25% requires a
reduction of the signal by 1/4 of its initial value to produce a fire.
The fault states to be manually recovered from are faults occurring during normal
monitoring (dimmed by more than 90%, compensation limit reached, and out of
synchronization). Similarly to fires, these faults can be recovered from by pressing the
recovery button* on the receiver.
*The conditions for manual recovery are specified in clause 6. If the conditions are unmet,
use manual recovery.
5.5. Total obscuration of the beam
If the beam detector is totally obscured, a fault signal will be produced. The fault condition
will disappear when the total obscuration condition is removed. The operation type can be
set with SW4 (refer to figure 11).
5.6. Automatic compensation for change of receiver's
signal strength
From the time that the beam detector is initialised, the signal at the receiver is checked
every 20 minutes for variation and will be altered by
±
1% back towards the original stored
value. The beam detector will store the initialisation value, when either the cover is closed
after the sensitivity has been set (sensitivity not in the no operation position). If the
power is turned off and back on with the receiver cover closed, the compensation
percentage before the power was turned off will be read from the internal memory and
the operation will continue. The compensation percentage can be cleared either by
opening the receiver cover while being energized or by turning the power on with the
receiver cover open.
