80 • CANopen
Network
Architecture
WAGO-I/O-SYSTEM
750
CANopen
RT
RT
CAN_High
CAN_Low
RT = 120 Ohm
GND
ohmmeter
Fig. 4-3: Measuring principle to check the CAN bus prior to wiring
g012445e
Measurement
Value
Meaning
infinite ok.
GND and CAN_L
0
Short-circuit between GND and CAN_L
infinite o.k.
GND and CAN_H
0
Short-circuit between GND and CAN_H
ca. 60
Ω
o.k., 2 terminal resistors in the bus
ca. 120
Ω
Only 1 terminal resistor in the bus
CAN_L and CAN_H
< 50
Ω
More than 2 terminal resistors in the bus
The CAN bus is 2-wire bus and bus error management can detect a cable
break or a short-circuit by the asymmetric operation.
Further information
The CiA provides documents regarding specifications, especially cable specifi-
cations in the Internet under: