ENGLISH
Pag. 37
1. The RS485 serial bus must be connected with an EIA RS 485 connection wire: No. 2 wi-
res with 0.22/0.35 mm2 section with shield (TWISTED PAIR). Nominal capacity between
conductors < 50 pF/m, nominal impedance 120 ohm. Total line length with this type
of connection must not exceed 1,000 metres. An example of a recommended cable is
a BELDEN 9841 or similar wire (EIA RS485 data transmission wire). Only connect detec-
tors (and IN and OUT modules) in a “cascading” manner. Avoid tree or star connections
since they reduce interference immunity.
2. The power supply to the detectors (and IN and OUT modules on the bus) must be con-
nected 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).
Note: each detector connected on the RS485 line must have its own univocal address betwe-
en 1 and 255 (247 for the ModBus protocol). Please see the gas detector technical manual
for address settings.
The diagram below shows the connection of IN and OUT detectors and remote modules on
the RS485 bus of the gas control unit.
IMPORTANT!
