
Doc# E149701 5 - 4
5: Communication Installation
Electro Industries/GaugeTech
The Leader In Power Monitoring and Smart Grid Solutions
Electro Industries/GaugeTech
The Leader In Power Monitoring and Smart Grid Solutions
Termination Resistors may not be needed. When they are used, the value of the
Termination Resistors is determined by the electrical parameters of the cable.
Figure 5.4 shows a representation of an RS485 Daisy Chain connection. Refer to
Section 5.1.2.1 for details on RS485 connection for the Unicom 2500.
Figure 5.4: RS485 Daisy Chain Connection
Figure 5.5: Incorrect “T” and “Star” Topologies
Twisted pair, shielded (SH) cable
R
T
+ - SH
R
T
+ - SH
+ - SH
+ - SH
Slave device 1
Slave device 2
Last Slave device N Master device
Earth Connection, preferably at
single location
Twisted pair, shielded (SH) cable Twisted pair, shielded (SH) cable
Twisted pair, shielded (SH) cable
+ - SH
+ - SH
+ - SH
Slave device 1
Slave device 2
Last Slave device N Master device
Earth Connection, preferably at
sin
le location
Twisted pair, shielded (SH) cable Twisted pair, shielded (SH) cable
Twisted pair, shielded (SH) cable
+ -SH
Twisted pair, shielded (SH) cable
Twisted pair, shielded (SH) cable Twisted pair, shielded (SH) cable
+ - SH
+- SH
+ - SH + -SH
Master device
Slave device 1 Slave device 2
Slave device 3 Slave device 4
R
R
+ - SH
Long stub results “T” connection that can cause
interference
roblem!
“STAR” connection can cause interference
roblem!
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