Emerson XM678D, Руководство по эксплуатации и установке

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MODBUS Termination Blocks ECT MODBUS Networking to E2s • 43
For MODBUS network wiring of XM678D
controllers to E2, Belden #8641 ( P/N 135-8641 ) is the
recommended wire type to use.
If the recommended cable is not available in your
area, be sure the wiring meets or exceeds the
following specs:
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
23.4.MODBUS Termination
Blocks
Because the XM678D 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 38 of the
device, keeping the exposed shield wire length as
short as possible (3 inches ideal maximum length).
Figure 23-10 - MODBUS Termination Block (P/N 535-2711)
SHIELD WIRE
(CONNECT TO
OF LAST DEVICE)
PIN 38
FROM OTHER
DEVICES
TO LAST DEVICE
AT END OF DAISY
CHAIN