19
Kamstrup A/S • 5512853_C1_GB_01.2017
M-Bus Master MultiPort 250D
4.3.1
Cable
The cable resistance and capacity must be as low as possible. The thicker the cable, the lower the resistance. The
thicker the cable, the higher the capacity.
An M-Bus cable must as a minimum be able to handle 50 V and 500 mA.
Diameter (mm ø)
Cross section (mm
2
)
Resistance in Ohm
per 1,000 metres
Length in metres per Ohm
0.5
0.20
90
11
0.65
0.33
53
19
0.8
0.50
35
29
1.0
0.79
23
45
1.13
1.00
18
57
1.26
1.25
14
71
1.39
1.52
12
87
1.6
2.0
8.7
115
Examples of resistance in copper cable.
Please note that the resistance in copper depends on its purity. The purer the copper, the lower its resistance.
LiYY
2x0.34 mm
2
2x0.50 mm
2
2x0.75 mm
2
2x1.0 mm
2
2x1.5 mm
2
Current load
Max 4.5 A
Max 6 A
Max 10 A
Max 12 A
Max 18 A
Cable resistance
56 Ω/km
39 Ω/km
26 Ω/km
20 Ω/km
12 Ω/km
Capacity
110 nF/km
120 nF/km
120 nF/km
120 nF/km
120 nF/km
J-Y(St)YY
2x0.60 mm
2
2x0.80 mm
2
Current load
-
-
Cable resistance
65 Ω/km
37 Ω/km
Capacity
120 nF/km
100 nF/km
Examples of cable types.