MT3401E.doc rev.0
21/05/13
Pagina 12 di 86
4 conductors are required for device connections (meaning both Smart P detectors and IN and
OUT modules): 2 for the RS485 serial bus and two for device power. For this reason, two
different wires must be used or a single wire that has suitable characteristics, described below.
-) The RS485 serial bus must be connected with an EIA RS 485 connection wire: No. 2
conductors with 0.22/0.35 mm
2
section + 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 meters. An example of a recommended wire is a BELDEN
9841 or similar wire (EIA RS485 data transmission wire). Only connect detectors (and IN and
OUT modules) in cascade. Avoid tree or delta connection 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).
The different Mu+S1 unit versions can support a different number of detectors from 64
to 256.
Each device connected on the unit's RS485 bus must have its own univocal address. STG/IN8
S and STG/OUT16-S module address settings are described later in this manual. See the
manual of the detector for its address settings.
Note: for the MTS++S1 256 version, the maximum number of connectible points on a single bus
is 128.
2.2.1)
Detectors connection
Gas detectors can be connected to the MU+S1 control panel 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 modules 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 unit will send a data signal on the RS485 line. This signal
is referring to its range (i.e. 0-300 ppm, 0-300 ppm, 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.
