Rockwell Automation Publication 450L-UM001D-EN-P - December 2019 99
Installation and Wiring Chapter 6
Functional earth is intended to reduce the high frequency (RF) noise and is also
known clean earth. The functional earth should carry only returning RF noise
currents. Ground schemes must include a functional earth ground to minimize
common mode disturbances that may have been capacitively coupled between
cables, transients on the 24V common, or radiated noise. Functional earth must
be separated from other earths and should be connected to protective earth at
one point.
The 450L 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.
Figure 62
shows the symbols that are used to designate functional and protective
earth grounds.
Figure 62 - 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 Ta b le 1 9
and
Table 20 on page 59
.
Figure 63 - Connect the Contact Elements to the EDM Input
IMPORTANT EDM function is not available for GuardShield safety light curtain with
receiver M12 5-pin plug-in (ArmorBlock Guard I/O connectivity).
Surge suppression elements are often required for the contactors depending
on the contactor.
Functional earth Protective Earth
Tx Rx
K1
24V DC
K2
P4
P4
24V DC
P5
0V
K1 K2
P5
K1
K2
0V
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