K&R GT600-4T132G User Manual page 264

8. Peripherals and Options
8
- 262 -
- 262 -
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Terminal wiring
–
Terminal wiring if node has CGND
GT60TX1 has three cables to connect 485+, 485- and CGND terminals
respectively. Check that RS485 bus on site has these three cables and terminals
are not connected reversely or wrongly.
If a shielded cable is used, shield must also be connected to CGND. Except
CGND, prevent shield from touching anywhere of the drive including drive housing
and grounding terminal.
Due to cable attenuation, if connection length is larger than 3 m, use AGW26
or a thicker cable. Always use a twisted pair cable to connect 485+ and 485-
respectively.
Non-shielded multi-core twisted pair cable and STP cable are recommended. If
non-shielded multi-core twisted pair cable is used, take twisted pair to connect
485+ and 485- and twist the unused cables into one rope and connect it to CGND.
If an STP cable is used, connect twisted pair to 485+ and 485- respectively and
shield to CGND. Shield can be connected to CGND only. It must not be connected
to ground.
485+
4
8
485-
5
node
CGND
–
Terminal wiring if node does not have CGND
For nodes without CGND, do not connect CGND cable or shield to PE of node
directly.
4
485+
8
5
485-
node
Take the following steps to handle it.
Step 1: Check whether a common reference ground of 485 circuit exists on other
ports of this node. If yes, connect CGND cable or shield to the pin.
Step 2: Check whether reference ground of 485 circuit exists on board of node. If
yes, connect CGND cable or shield to it.
Step 3: If reference ground of 485 circuit is not found, keep CGND cable or shield
unconnected and use an extra ground cable to connect this node to PE of other
nodes.
●
Transmission Distance
Maximum number of nodes and transmission distance of standard RS485 circuit vary
with different baud rates, as listed in the following figure:
No. Baud Rate Max. Transmission Distance Number of Nodes Cable Diameter
1 115.2 Kbps 100 m
2 19.2 Kbps 1000 m
For details of the Modbus communication protocol, see
.
4
8
5
node
Non-shielded
multi-core cable
4
8
5
node
CGND cable
unconnected
128
128
485+
485-
STP cable
CGND
485+
485-
Shield
unconnected
AWG 26 (0.1 mm
AWG 26 (0.1 mm
2
)
2
)