SENSITRON
A Halma Company
MT4984
MU+ PK-32
Manual (EN)
P. 45/14
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Detectors with 4-20 mA output connected to STG/IN8-PK
input module
The following diagram illustrates connections between a 4-20mA gas
detector and a STG/IN8-PK input module. When starting the system,
make sure minimum 12 Vdc voltage reaches each gas detector.
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Detectors with RS485 output
Gas detectors provided with RS485 serial communication are con-
nected directly to the RS485 bus of the MU+PK-32 gas con-
trol unit. The STG/IN8-PK input module and STG/OUT16-S output
module are also connected to the RS485 bus.
The maximum length for this communication is 1000m.
4 conductors are needed for this type of connection: two for the RS485
serial and two for the power supply of the device. For this reason, we
suggest that two different wires or a single wire with the features de-
scribed below, is used.
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The RS485 serial bus must be connected with an EIA RS 485 connec-
tion wire: No. 2 wires with 0.22/0.35 mm2 section with shield (TWISTED
PAIR). Nominal capacity between conductors < 50 pF/m, nominal im-
pedance 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 detectors (and IN and OUT modules) in a “cascading” manner.
Avoid tree or star connections since they reduce interference
immunity.
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The power supply to the detectors (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 techni-
cal manual enclosed with gas detectors for this purpose).
Please note
Each detector connected on the RS485 line must have its own univocal address.
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.
Figure 9
Connection of the 8 detectors of the STG/IN8-PK module
+ -
S
Input 1
Input 2
Input 3
Input 4
Input 5
Input 6
Input 7
Input 8
0
0
1
4
OFF
ON
V-
V+
B
A
V-
V+
V+
V-
