Kamstrup M-Bus Master MultiPort 250D - Cable Topology

20 Kmstrup A/S • 5512853_C1_GB_01.2017
M-Bus Mster MultiPort 250D
In big networks using secondry ddressing, worst cse
lod must be considered s 250 slves of 1 UL (Unit Lod)
ech drwing 5.4 A, which thin cbles will not be ble to
withstnd.
Plese note tht resistnce cn be stted in two different
wys in cble specifictions, i.e. s cble resistnce or s
loop resistnce.
Loop resistnce is the totl resistnce mesured through
the two conductors. Cble resistnce is the resistnce
through one conductor. Therefore, loop resistnce is
lwys twice the cble resistnce.
Mesurement of loop resistnce.
Mesurement of cble resistnce.
4.3.2 Cble topology
An M-Bus network normlly uses bus or str topology or  combintion of both.
The dvntge of bus topology is shorter wires. The disdvntge is tht  cble interrupt will men tht ll the
following meters cn no longer be red.
The dvntge of str topology is the fct tht ll the other meters cn still be red fter  cble interrupt. The
disdvntge is  lrge consumption of cble with  high leding lod, which reduces the mximum cble length nd
mkes  reduction of communiction speed necessry, respectively.
Bus topology offers two solutions. One solution is to loop the cble through ech meter. This solution presupposes tht
there is room for two cbles nd tht the connection terminls re prepred for the connection of two sets of cbles. All
connections re thereby typiclly mde inside the meter.
The other solution is to use bus topology with ech individul meter connected to the bus. With this solution,  number
of connections must be estblished on the bus itself.