(and IN and OUT modules) in a "cascading" manner. Avoid tree or star connections since
they reduce interference immunity.
-) Detector power supply (and IN and OUT modules on the bus) must be connected with
a 2- core wire with adequate section based on the number of connected devices, their
distance from the power supply and each device’s consumption (please see the technical
manual enclosed with gas detectors for this purpose).
Each device connected on the unit's RS485 bus must have its own univocal address. See
the appropriate section of this manual to set the address of the STG/IN8 S and
STG/OUT16-S modules, and see the relative manual for setting the detector address.
2.2.1 Detector connection
Gas detectors can be connected to the MULTISCAN 8+ central unit in two different ways,
based on the detector output signal.
1) 4-20 mA analogue proportional output.
The detector connected to the unit and ST.G/IN8 S module will send a 4-20 mA signal
referring to its range (i.e. 0-300 ppm, 0-30 ppm, 0-100% LEL etc.) and the unit, suitably
programmed, will display the relevant gas concentration indication measured by the
detector and consequently activate the alarms when the set values are reached.
2) RS485 digital proportional output
The detector connected to the central unit will send a data signal on the RS485 line. This
signal refers to the range of the detector (i.e. 0-300 ppm, 0-30 ppm, etc.); the unit,
suitably programmed, will display the relevant gas concentration indication measured by
the detector and consequently activate the alarms when the set values are reached.
Detectors with 4-20mA output
Detectors with 4-20mA analogue output are either connected to the central unit,
directly on the main board or via one remote 8-input STG/IN8-S module. The module
may be connected remotely to the central unit. For connection, a detector with a 4-
20mA analogue output requires a 3-conductor cable: 2 conductors for the power supply
(usually from 12 to 28 Vdc - refer to the gas detector technical manual) and one
conductor for the 4-20mA signal. The generally recommended cable is a shielded 3 x
0.75, which allows up to 100 meters between the gas detector and STG/IN8-S input
module
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