Rs485 Daisy Chain Connection; Incorrect “T” And “Star” Topologies - Electro Industries Shark 200 Installation & Operation Manual

• Termination Resistors (RT) may be needed on both ends for longer length transmis-
sion lines. However, since the meter has some level of termination internally,
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.
Master device
R
T
SH + -
Twisted pair, shielded (SH) cable
Earth Connection, preferably at
single location
Master device
R
T
SH + -
Twisted pair, shielded (SH) cable
Earth Connection, preferably at
single location
Slave device 1
SH +
SH +
Slave device 3
Electro Industries/GaugeTech
Electro Industries/GaugeTech
The Leader In Power Monitoring and Smart Grid Solutions
The Leader In Power Monitoring and Smart Grid Solutions
Slave device 1
SH + -
Twisted pair, shielded (SH) cable
Figure 5.4: RS485 Daisy Chain Connection
Slave device 1
SH + -
Long stub results "T" connection that can cause
interference problem!
Twisted pair, shielded (SH) cable
Twisted pair, shielded (SH) cable
-
Master device
-
Twisted pair, shielded (SH) cable
Figure 5.5: Incorrect "T" and "Star" Topologies
5: Communication Installation
Slave device 2
SH + -
Twisted pair, shielded (SH) cable
Slave device 2
SH + -
Twisted pair, shielded (SH) cable
Twisted pair, shielded (SH) cable
- + SH
"STAR" connection can cause interference
SH + -
problem!
SH + -
Twisted pair, shielded (SH) cable
#
Doc E149701
Last Slave device N
R
T
SH + -
Last Slave device N
R
T
SH + -
Slave device 2
Slave device 4
5-4