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Kamstrup A/S • 5512853_C1_GB_01.2017
M-Bus Master MultiPort 250D
The master’s display shows that it is
configured as a repeater.
When the master is configured as a
repeater, only the menu points which
can be used with this configuration
are displayed.
250D configured as repeater.
Main menu when 250D is configured as
repeater.
If the repeater is not connected to a master or repeater via terminals 53
and 54, the symbol shown in the top right-hand corner is displayed.
Note:
The power supply MUST be switched off during reconfiguration
between master and repeater.
4 Cabling
Typically unshielded twisted pair cable up to approx. 1.5 mm
2
is used. The cabling topology is typically star or bus or a
combination of both. The connection in M-Bus is independent of polarity and no termination resistance at the end of
the cabling is needed.
If a cable type with shield is used, it is important that the two M-Bus conductors are not connected to ground or shield.
No precise indication as to maximum cable length in an M-Bus network can be given as it depends on various
parameters.
The two most important parameters to consider when selecting cable for an M-Bus installation are cable resistance
and cable capacity. Generally speaking, the resistance limits the number of M-Bus slaves, and the capacity limits the
communication speed.
Furthermore, we recommend keeping a certain distance between M-Bus cables and other cables in order to minimize
noise from high-power electric machinery.