Wire Connection; Can Bus Wire Connection - ICP DAS USA I-7242D User Manual

2.2

Wire Connection

2.2.1

CAN bus wire connection

In order to minimize reflection effects on the CAN bus line, the CAN bus
lines have to be terminated at both ends by two terminal resistances. Based on
the ISO 11898-2 spec, each terminal resistance is 120Ω (or between
108Ω~132Ω). The length related resistance should have 70 mΩ/m. Users
should check the resistances of their CAN bus, before they install a new CAN
network as figure 2-2.
Moreover, to minimize the voltage drop on long distance, the terminal
resistance should be higher than the value defined in the ISO 11898-2. Table
2-1 may be used as a reference.
Table 2-1 Relation between bus cable and length
Bus
Length
(meter)
0~40
40~300
300~600
600~1K
I-7242D DeviceNet/Modbus RTU Gateway User's Manual, July 2006, Version 1.1
Figure 2-2 CAN Bus Wire Connections
Bus Cable Parameters
Length Related
Resistance
(mΩ/m)
70
< 60
< 40
< 20
Cross Section
(Type)
0.25(23AWG)~
2
0.34mm (22AWG)
0.34(22AWG)~
2
0.6mm (20AWG)
2
0.5~0.6mm
(20AWG)
2
0.75~0.8mm
(18AWG)
I-7242D user manual
Terminal
Resistance
(Ω)
124 (0.1%)
127 (0.1%)
150~300
150~300
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