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Xedge Chassis Systems
Xedge 6640/6645 Ground Connections
At the Xedge 6640/6645 chassis rear panel, make connections to the following terminals as required
for your site/applications:
•
A shorting bar at the rear panel, below the alarm and status input connectors can be used for the
connection, separation, or isolation of frame and signal grounds as required.
•
Two pem nuts located above the alarm and status input connectors can be used for connection
to frame ground as required.
At the Xedge 6645 chassis rear panel, a 9-position terminal block can be used for connection to
frame and signal ground. Two terminals provide connection to frame ground; one terminal provides
connection to signal ground. Connections to these terminals are optional.
Grounding Options
To connect frame and signal grounds:
1. Loosen both ground screws.
2. Slide the shorting bar fully to the left.
3. Tighten both ground screws.
To separate frame and signal grounds:
1. Loosen both ground screws.
2. Slide the shorting bar fully to the right.
3. Tighten both ground screws.
4. Connect the frame ground to a ground connection at the site.
To isolate frame and signal grounds:
1. Loosen both ground screws.
2. Slide the shorting bar fully to the right.
3. Connect a 100-ohm, 1-W resistor between the ground screws.
4. Tighten both ground screws.
Grounding Guidelines
It is common practice to connect chassis and signal ground together (this is the default selection).
Signal ground is the 0 V reference for the digital circuits contained in the chassis and the reference
for unbalanced data interfaces such as EIA/TIA-232-E and RS-423. Connecting grounds helps
prevent AC power line noise, but a large ground current can flow in the shield of a cable if it is
connected between equipment grounds that have different potentials.
To avoid this problem:
•
Check that the potential difference between grounds is less than 0.25 V RMS.
•
Break the continuity of the shield in the middle of a long cable run.
•
Connect the shield to ground at only one end.
•
Separate the signal and chassis grounds.
•
Isolate the signal and chassis grounds with a 100-ohm, 1 watt resistor (this limits the current in
the signal ground leads and helps prevent AC power line noise).
5. Some local electrical codes and equipment manufacturers require separation of signal and
chassis grounds. In this case, you have to separate the grounds and connect the frame ground
to a ground connection at the site.
032R440-000
Issue 17
Xedge 6000 Hardware
Installation & Setup Guide
Xedge 6640/6645 Chassis
2-39
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