Siemens SENTRON PAC2200, Product Manual, Page: 51 / 130

Connection
4.4 Connecting the communication cable
PAC2200
Equipment Manual, 12/2019, L1V30415167B-03
49
4.4.2 RS485 communication cable
This interface is available as an option.
Always use a shielded cable for the RS485 data cable. The data is transmitted differentially
via two wires -/A and +/B. The third wire "COM" serves as the common ground potential.
1. Connect the cables Com, +/B and -/A to the appropriate screw terminals on the terminal
block.
2. Provide sufficient mechanical strain relief for the RS485 cable.
3. Ground the shield of the cable (see chapter Grounding of the Ethernet/RS485 cable
(Page 50)).
4. On the first and last communication nodes, switch a bus terminating resistor between -/A
and +/B.
Grounding of the COM line:
Many masters do not have a common terminal. If this is the case, then RS485 common
should reference the same functional ground as the master (at a single point). If the master
has a common terminal, then the common is connected to it, and it is not connected to
functional ground.
4.4.3 M-Bus communication cable
This interface is available as an option.
An unshielded two-wire line can be used for an M-Bus data cable.
1. Connect the + and - cables to the appropriate screw terminals on the terminal block.
2. Provide sufficient mechanical strain relief for the M-Bus cable.