I/O Module Installation and Wiring - Terminal Block-to-Field (Signal) Wiring
60 HC900 Hybrid Controller Installation and User Guide Revision 5
9/03
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 27. 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 27 - 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 28. 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 28.
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 28 - Wire-Shield Grounding
