6.4 Electrical Grounding
●
For CAN devices with electrical isolation the CAN_GND must be connected between the
CAN devices.
●
CAN_GND should be connected to the earth potential (FE) at
exactly one
point of the
network.
●
Each
CAN interface with electrical connection to earth potential
acts as a grounding point.
For this reason it is recommended not to connect more than one
CAN device with electrical
connection to earth potential.
●
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
When using the CAN-Repeater the theoretical values of the reachable wire length with
esd module shown in table 5 is
reduced by 14 m
.
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
the cross-section
according to
CiA 303-1
[mm²]
1000
37
25
0,25 to 0,34
800
666,6
500
333,3
250
59
80
130
180
270
50
-
100
-
250
0,34 to 0,6
166
125
420
570
-
500
0,5 to 0,6
100
83,3
66,6
50
710
850
1000
1400
650
-
-
1000
0,75 to 0,8
33,3
20
12,5
10
2000
3600
5400
7300
-
2500
-
5000
not defined in
CiA 303-1
Table 5:
Recommended cable lengths at typical bit rates (with CAN-Repeater)
●
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.
Page 22 of 28
Hardware Manual • Doc. No.: C.1330.21 / Rev. 1.4
CAN-Repeater
