This article describes how the galvanic isolation affects the network for CAN Interface boards, CAN-Repeaters and CANbridges.
CAN repeater, CANbridge, CAN interface board
How affects the galvanic isolation my network?
The galvanic isolation improves the stability and quality of the CAN signal and protects the CAN controller and thus the device from damages caused by overvoltage coming from electromagnetic interferences or different electric potentials in the network using different power supplies for each device.
On the other hand, a galvanic isolation is an additional component in the communication path between CAN controller and CAN bus. Even fast components have delay times in the 50 ns range. This roughly corresponds to the signal propagation time of a 10 meter cable and must be considered by calculating the maximum cable length.
However, usually the benefits of a galvanic decoupling outweigh the disadvantages.