User guide

Wiring and Cabling
136
890 USE 108 00 August 2001
System Reference Grounding
System
Grounding
Overview
The masked copper grid on the primary DTA 200 housing’s circuit board is the
system reference ground. If the DTA 200 housing is mounted on the DIN rail, the
functional ground and system reference ground are connected together (only with
the Z screw installed with the fiber washer on top and the metal washer on the
bottom against the housing). This creates a closed circuit whereby the system
reference ground is established. All DTA 200 housing’s are shipped from the factory
with the circuit closed. This is accomplished by the Z screw and washers, which
makes physical connection between the system reference ground and the spring
clips that complete the connection to functional ground.
The following figure shows the ground connections on a DTA 200 primary
backplane.
Only the DTA 200 primary backplane can provide the Z screw connection to the
system functional ground on the DIN rail. The DTA 201 and DTA 202 secondary
backplanes do not have Z screws.
Note: If local environmental conditions warrant, you can, optionally, remove the Z
screw to provide isolation between the reference and functional grounds.
Reference and functional grounds are routed through an RC filter rather than
directly coupled either when the Z screw is installed (only with the Z screw installed
with the metal washer on top and the fiber washer on the bottom against the
housing), or if both the Z screw and both washers are removed. Either way an open
circuit is created.
DIN Rail
(Functional
Ground)
Z screw
Reference
Ground Point
Ground-Contact
Through-Holes