Installation guide

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ground reference. Transclinics equipment have a floating (isolated) RS485 inputs (in other words, not con-
nected to earth), but other equipment might be connected to ground or they could induce residual voltages.
Therefore recommend that the 485 communications line for Transclinics equipment be independent of other
equipment to prevent problems arising from incompatibilities. If equipment from a third party manufacturer
must be installed, review the characteristics carefully with the manufacturer and understand that Weidmuller
cannot be responsible for any resulting communication problems.
5.2.5 Data Cables
Generally a twisted pair is used with one conductor for signal A and the other one for signal B. Twisted pair
is used since they provide better immunity to electromagnetic interference. This is essential to guarantee a
proper communication at long distances.
Usually, one cable with several pairs is used for a 3 wire RS485 communication where one pair is used for
transmitting signals and another conductor of a different pair is used to interconnect the signal GNDs of the
devices.
Fig. 10 Example of RS485 cables for 3 wire communications
Weidmuller recommends using twisted pair cable to guarantee a better signal and prevent communication
problems. Cable gauges larger than AWG24 are recommended (AWG22 is a good option) and cable with a
shield to improve noise resistance. Larger gauges provide better communication. There are manufacturers
that provide specific solutions for RS485 industrial communications. Weidmuller recommends consulting with
a specialist to select the most ideal cable type.
5.2.6 Network Topography
The RS485 communication is designed for what is called a Daisy-Chain configuration, which consists in in-
terconnecting the lines of the different devices linking them together as shown in the following figure.
Fig. 11 Proper RS485 network topology (Daisy-Chain)
Other types such as the tree or star types should not be used although a tree type structure may be valid as
long as the length of the stubs is kept to a minimum. In other words, a stub measuring several centimetres
can be used but not one measuring several metres. The stubs can cause signal reflections (when they are