Wiring Notes
Manual • Doc.-No.: C.3034.21 / Rev. 1.2
CAN-CBX-THERMO
Page 40 of 123
6.4 Electrical Grounding
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For CAN devices with electrical isolation the CAN_GND must be connected between the CAN
devices.
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CAN_GND should be connected to the earth potential (FE) at exactly one point of the network.
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Each CAN interface with electrical connection to earth potential acts as grounding point.
For this reason it is recommended not to connect more than one CAN device with electrical
connection to earth potential.
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Grounding can be made e.g. at a termination connector (e.g. order no. C.1302.01 or C.1301.01)
6.5 Bus Length
NOTICE
Please note that the cables, connectors and termination resistors used in CANopen
networks shall meet the requirements defined in ISO11898-2. In addition, further
recommendations of the CiA, like standard values of the cross section, depending on the
cable length, are described in the CiA recommendation CiA 303-1
(see CiA 303 CANopen
Recommendation - Part 1: „Cabling and connector pin assignment“, Version 1.8.0, Table 2).
Bit-Rate
[kBit/s]
Theoretical values of
reachable wire length with
esd interface l
max
[m]
CiA recommendations
(07/95) for reachable wire
lengths l
min
[m]
Standard values of
cross-section
according to CiA 303-
1 [mm²]
1000
37
25
0.25 to 0.34
800
59
50
666 6
.
80
-
500
130
100
0.34 to 0.6
333 3
.
180
-
250
270
250
166
420
-
0.5 to 0.6
125
570
500
100
710
650
83 3
.
850
-
0.75 to 0.8
66 6
.
1000
-
50
1400
1000
33 3
.
2000
-
not defined in
CiA 303-1
20
3600
2500
12.5
5400
-
10
7300
5000
Table 12: Recommended cable lengths at typical bit rates (with esd-CAN interfaces)
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Optical couplers are delaying the CAN signals. esd modules typically reach a wire length of 37 m
at 1 Mbit/s within a proper terminated CAN network without impedance disturbances like e.g.
caused by cable stubs > 0.3 m.