MODBUS Termination Blocks ECT MODBUS Networking to E2s • 25
If the recommended cable is not available in your area, be
sure the wiring meets or exceeds the following specs:
18.5.MODBUS Termination
Blocks
Because the XR75CX device has no on-board means of
termination, use the MODBUS termination block (P/N
535-2711) for termination that can be wired to the end of
the cable segment using the three-pin connector. Wire the
two signal wires to the outside terminals, and connect the
shield to pin 18 of the device, keeping the exposed shield
wire length as short as possible (3 inches ideal maximum
length).
Shielded? Yes
Conductor Type Twisted Pair
Gauge 18 - 24 AWG
Capacitance between
signal wires
31 pF/ft or less
(9.45 m) or less
Capacitance between
signal and shield
59 pF/ft or less
(17.98 m) or less
Maximum Length
4000 ft/18 to 22 AWG
(1219.2 m)
2500 ft/24 AWG
(762 m)
Nominal Impedance 120W±50W
Figure 18-9 - MODBUS Termination Block (P/N 535-2711)
SHIELD WIRE
(CONNECT TO
OF LAST DEVICE)
PIN 18
FROM OTHER
DEVICES
TO LAST DEVICE
AT END OF DAISY
CHAIN
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