Siemens SENTRON PAC2200 - RS 485 Communication Cable; M-Bus Communication Cable; Grounding of the Ethernet; RS 485 Cable

Connection
4.4 Connecting the communication cable
PAC2200
46 Manual, 05/2018, L1V30415167B-02
4.4.2
RS 485 communication cable
This interface is available as an option.
Always use a shielded cable for the RS 485 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 RS 485 cable.
3. Ground the shield of the cable (see chapter 4.4.4 Grounding of the Ethernet / RS 485
cable).
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 RS 485 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.
4.4.4
Grounding of the Ethernet / RS 485 cable
NOTICE
The upper limit values will be violated if the cable is not grounded.
Compliance with the technical limit values for noise radiation and noise immunity is only
guaranteed if the cable is correctly grounded. The operator of the system is responsible for
ensuring compliance with the statutory limit values (CE mark).
Make a shield connection on both sides as described here.