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Rockwell Automation Publication 450L-UM001F-EN-P - March 2022
Chapter 6 Installation and Wiring
Grounding
There are two types of recommended grounding for 450L safety light curtains:
•
Protective earth (PE)
•
Functional earth (FE)
Protective earth is intended to help protect personnel from electric shock.
Protective earth is also known as dirty earth as it can contain many types of
noise transients and stray currents. The 24V common side of the 24V power
supply must be connected to protective earth at one location.
Functional earth is intended to reduce the high frequency (RF) noise and is
also known clean earth. The functional earth must carry only returning RF
noise currents. Ground schemes must include a functional earth ground to
minimize common mode disturbances that were capacitively coupled between
cables, transients on the 24V common, or radiated noise. Functional earth
must be separated from other earths and must be connected to protective
earth at one point.
The 450L safety light curtain plug-in modules have a pin that is labeled
functional earth and a pin that is labeled 0V (GND). The 0V (GND) must be
connected to the 24V common. At some point, the 24V Com is connected to
protective earth. In the absence of electrical noise, the functional earth could
be connected to 24V Com or directly to protective earth point. In the presence
of electrical noise, the functional earth connection becomes critical; the
connection must be made to return the noise to its source in as short a
distance as possible.
shows the symbols that are used to designate functional and
protective earth grounds.
Figure 67 - Earth Symbols
External Device Monitoring (EDM) Connection
The External Device Monitor (EDM) describes the EDM feature. The EDM
function can be performed with the receiver plug-ins according to
and
Figure 68 - Connect the Contact Elements to the EDM Input
Functional earth
Protective Earth
Tx
Rx
K1
24V DC
K2
P4
P4
24V DC
P5
0V
K1
K2
P5
K1
K2
0V
