CTI 2550-A, Installation And Operation Manual

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18 C T I 2550-A Installation and O peration G uide
2.5.1 Connecting Voltage Input Wiring
For voltage input circuits, connect the signal wire to the +IN (positive) screw terminal, and the return
wire to the -IN (negative) screw terminal. Insert the wires in the appropriate holes on the front of the
connector. When the wires are inserted, tighten the screws. Repeat this procedure for the remaining
voltage input channels.
2.5.2 Connecting Current Input Wiring
For current input circuits, connect the signal wire to the +IN (positive) screw terminal, and the return
wire to the -IN (negative) screw terminal. Insert the wires in the appropriate holes on the front of the
connector. When the wires are inserted, tighten the screws. Repeat this procedure for the remaining
current input channels.
2.5.3 Connecting the Shield Wiring
Control Technology Inc. recommends that all wires be shielded twisted pair with a foil wrap shield and
a separate drain wire and that they be installed in a metallic conduit. Use Belden cable 8761 or
equivalent which contains a foil wrap shield and a separate drain wire. The shield and the foil wrap
should be twisted together and should be terminated at only one end. The other end should be left in an
open circuit condition. CTI recommends that the shield be terminated at the PLC end of the signal wire.
Special components are installed on the module to aid in the rejection of noise.
When entering the industrial cabinet the shield should be routed from the main terminal strip all the
way to the PLC. Signal leads that do not maintain a shield from the terminal strip to the PLC act as
antennas and are susceptible to radiated and conducted emissions in the cabinet. Unprotected cables
may introduce measurement errors in the module.
The front connector on the module contains a G terminal which may be used for the shield wire if the
installation is in a noise free environment. If the installation is in an extremely noisy environment CTI
strongly recommends that the shielded wires terminated to the PLC chassis ground.
CTI has exhaustively tested this product to maximize its ability to reject noise from inductive sources
as well as showering arcs, fast transients and other high frequency generators and has determined that
the test best performance results from connecting all shield wires together at the PLC module and
terminating this single wire to the chassis ground with a large current capacity conductor. CTI
recommends using a #8 gauge wire are larger from the PLC chassis tothe earth ground connection.