Control Panel Design Guidelines
Pay careful attention to the placement of system components and associated cable routing. These items can significantly
enhance the performance and integrity of your control application.
Control Panel Grounding
The control panel should be connected to a good, high-integrity earth ground both for safety considerations and shielding
purposes. Maple Systems cannot overemphasize the importance of good grounding. If you fail to use good grounding
procedures during installation, sporadic malfunction of the OIT may occur:
• Connect the OIT’s chassis ground terminal to a reliable earth ground with a low-resistance path.
• Route all earth ground wires that lead from the OIT, the PLC, the power supply, and the line filter to a central
earth ground point such as a barrier strip. This will ensure that no ground current from one device influences
the operation of the other devices.
• Connect the OIT chassis ground terminal to the control panel door using a heavy-gauge short braided cable
or ground wire to minimize resistance.
• Connect the power cable’s shield wire to the OIT’s chassis ground terminal.
• Connect the control panel to earth ground using a copper grounding rod close to the OIT and control panel.
Hinged doors on control panels do not provide a long-term electrical connection to the rest of the enclosure. Corrosion
develops over time and prevents good electrical contract. For this reason, a separate wire braid should be installed from the
hinged control panel to the rest of the enclosure.
For a more in-depth overview of ground wiring techniques, refer to technical note #1027,
OIT Ground Wiring and Electrical
Noise Reduction
, which you can find
at www.maple-systems.com
.
Connect OIT Chassis Ground to Control Panel
To reduce the possibility of electrical interference, connect the chassis ground terminal of the OIT to a clean earth ground. If
the control panel is metal, make sure it is properly grounded. Then connect a
short
heavy-gauge wire (#18 AWG) from the
chassis ground terminal of the OIT to a mounting bolt on the control panel door. The mounting bolt must have good
electrical contact to the control panel; scrape away any paint that may be covering the panel to provide a good connection.
1010-0300, Rev 02
Installation of OITs
9
Shielded DB9P
male connector
+24V
0V
+ -
BATTERY
EXTENSION
PORT
RS
-485
I / O control lines
PLC/Host
Ground wires
(rear side)
OIT is
grounded to
control panel
Ground
strap
Power
line
filter
Quiet ground
(isolated)
Quiet ground
Line
Filter
OIT
Power
Supply
Shielded power cable
Shielded
communication
cable
Control panel is
tied to a reliable
earth ground
OIT
Control Panel Example
