Revision 10 ControlEdge HC900 Process & Safety Controller User and Installation Manual 85
May 2019
Signal Grounding
The shield for each input should be grounded at
the grounding bar (optional) at the top or bottom
of each rack as indicated in Figure 44. For low-
frequency noise rejection, I/O wiring shields
should be grounded only at the controller end.
For high-frequency noise rejection, shields should
be grounded at the controller and at the field
device. If the ground voltage potential at the field
device is different from that at the controller, a
DC isolation capacitor should be used between
the shield and the grounding bar on the rack.
Figure 43 – Signal-Wire Grounding
Aluminum grounding bars for I/O wiring are available as options. When selected for use, they are
fastened to the top and/or bottom of each rack, as indicated in Figure 44. To enable connection of
multiple ground wires with a single screw, the wires can be twisted together and secured with a wire lug.
To facilitate module replacement, it is advisable in most cases to route all wiring through either the top or
the bottom of the terminal block. This
allows the terminal block to pivot up or
down, allowing ready access to the module,
and is the preferred method for a limited
number of wires.
For a larger number of wires, or for wires
of a heavier gauge, it is advisable to route
some wires through the top of the terminal
block, and some through the bottom, as
indicated in Figure 44. In this case, it is
necessary to adjust wire length so as to
ensure adequate flexibility of the twisted
wires and to provide clearance sufficient to
remove the I/O module.
Figure 44 – Wire-Shield Grounding
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