Danfoss DGS Series User Manual page 8

User Guide | Danfoss Gas sensor, type DGS
8 | BC291049702513en-000201
DGS with Modbus network communication in combination with other devices powered by more
than one power supply
It is strongly recommended to use direct current power supply when:
• more than 5 DGS units are powered by the same power supply
• the bus cable length is longer than 50 m for those powered units
It is moreover recommended to use class 2 power supply (see
Make sure to not interrupt the shield when connecting A and B to the DGS (see Fig. 4).
Busmaster
A
L
B
Danfoss
Shld
Modbus
230 V
N
device
AK-SM
Busslave
A
L
B
Danfoss
Shld
Modbus
230 V
N
device
AK-CC
Fig. 6: Wiring diagram for system with multiple power supplies
Ground potential difference between nodes of the RS485 network might affect the communication.
It is advised to connect a 1 KΩ 5% ¼ W resistor between the shield and the ground (X4.2) of any unit
or group of units connected to the same power supply (Fig. 6).
Please refer to Literature No. AP363940176099.
Power supply and voltage alarm
The DGS device goes into voltage alarm when voltage exceeds certain limits.
The lower limit is 16 V.
The upper limit is 28 V, if DGS software version is lower than 1.2 or 33.3 V in all other cases.
When in the DGS the voltage alarm is active, in the System Manager the "Alarm inhibited" is raised.
Shield
1 KΩ
DGS 1 + DGS 2 +
#adr n1 #adr n2
A A
B Gnd B Gnd
Shield
1 KΩ
DGS 1 + DGS 2 +
#adr n11 #adr n12
A A
B Gnd B Gnd
AK-PS 075)
AK-PS 075 power supply
+
DGS n +
#adr nx
A
–
B Gnd
AK-PS 075 power supply
+
DGS n +
#adr ny
A
–
B Gnd
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L
230 V
N
L
230 V
N