Rockwell Automation 1770-HT8 SMART TRANSMITTER - Manual (Page 43)

Installing the Smart Transmitter Interface
Products
Chapter 2
2-18
Grounding the Communications Controller and Terminal Block
Chassis
Because the Communications Controller and the Terminal Blocks can be as
far as 1000 feet apart it is best to ground each unit locally. To ground the
Communications Controller, connect a wire from the Earth Ground
terminal of its 3 position COMBICON power connector (see Figure 2.18)
to the local ground bus.
Ground each Terminal Block in the same way and insert the plug in the
power connection header for loop power (see Figure 2.19). Each Terminal
Block must be grounded in this way regardless of whether or not it is to
provide 4-20 mA loop power for HART field devices.
Grounding the HART Field Device Cable Shield
Connectors to the HART field devices on the Terminal Blocks are
internally grounded to the power connector. Once the power connector is
properly grounded, these connectors are also properly grounded.
Grounding the Analog I/O Cable Shield
Important: The shield connection in the cable between the Terminal
Blocks and the Analog I/O modules must be grounded at one end only. The
cable must not be more than 30 feet long.
If the Analog I/O module is a 1771-IFE module, ground the shield
connection to the chassis of the 1771-IFE as shown in the documentation
for that module. Do not ground the shield to the Terminal Block connector.
If the Analog I/O module is of another kind, and grounding at that end is
not feasible, you must first connect the cable’s shield wire to the position
on the Terminal Block plug marked SH for Shield (see Figure 2.17).
Grounding