Sensitron PL4 +D - Page 14

MT4412E Rev.2 15/10/2019 Pagina 14 di 30
Detectors with 4-20mA output
Detectors with 4-20mA analogue output are either connected to the gas control unit, directly on
the main board or via one remote 8-input STG/IN8-S module. The module may be connected
remotely to the gas control 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
Detectors with 4-20 mA output directly connected to the gas control unit
+V 1 2 3 4 -V
Fig. 2.2.1 a) Connection of the 8 detectors of the gas control unit
Detectors with a 4-20 mA output connected to the ST.G/IN8-S module
The following diagram shows the connection of a gas detector with a 4-20 mA output to a
STG/IN8-S input module. During system start-up, make sure that each gas detector reaches a
minimum voltage of 12 Vdc.
-V
I8
I7
I6
I5
+V
-V
I4
I3
I2
I1
+V
-V
B
A
+V
REMOTE INPUT
MODULE ST/G.IN8
(+V)
(-V)
(S)
Positive
Negative
4-20 mA signal
4-20 mA
analog
gas
detector
Rilevatore
analogico
4-20 mA
MODULO INGR.
4-20 mA ST/G.IN8
Fig. 2.2.1 b) connnection of the 8 detectors of the ST.G/IN8-S module