WAGO-I/O-SYSTEM 750
Connect Devices 37
753-649 M-Bus Master Module
Manual
Version 1.1.2
6.3.2
M-Bus Cable
If shielded cables are used, the cable shielding should be placed on the FE
connection of the M-Bus master.
The cabling of an M-Bus segment must meet the general requirements of
standard EN 13757-2. For reliable communication, the following values are
relevant and depend on each other in some cases:
• Total cable length: Sum of the lengths of all M-Bus cables connected to the M-
Bus master
• Master-to-slave distance: Cable length between the master and the most
distant slave
• Cable cross-section
• Baud rate
In general, the greater the cable length or the distance between the master and
slave is, the lower the baud rate is.
The supported combinations are given in the section “Technical Data” >
“Communication.”
Excessive cable lengths can trigger the overcurrent shutdown (see section
“Device Description” > “Overcurrent Shutdown”).
Although larger cable cross-sections decrease the voltage drop on the M-Bus
cable at large distances, they simultaneously increase the risk of triggering the
overcurrent shutdown of the M-Bus master.
6.3.3
M-Bus Network
One network with up to 40 M-Bus standard loads can be connected to each M-
Bus master and queried.
If the permissible number of M-Bus standard loads is exceeded, the M-Bus
master shuts down the power supply to the M-Bus slaves.
Only connect M-Bus slaves
Connecting additional M-Bus masters to the M-Bus master can lead to damage
to the device.
Only connect M-Bus members with slave characteristics to the M-Bus master.
