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General Environmental Considerations
Avoid installing EZ7 Series TouchPLC in areas where the following conditions may exist:
Environmental temperatures above or below those specified by the EZ7 Series TouchPLC
Prolonged exposure to humidity and liquids which may be sprayed or splashed on the equipment
Dusty environments where airborne particles may accumulate on equipment causing reduction of heat
dissipation and reduction in effective electrical spacing between components
Areas with excessive vibration
Areas with high-radiated electrical noise, such as near fields of transmitting antennas and areas in close
proximity of arc welding stations
Physical Layout in a Control Cabinet
When possible, cabinets housing electronic equipment should be designed with provisions for natural or forced
ventilation to facilitate heat dissipation. Observe the following rules for cabinet installation:
Heat generating equipment (power supplies and other heat inducing components) should be installed toward
the top of the cabinet. The lower space in the cabinet is cooler than the top area.
Install heat-sensitive components in the lower section.
Provide enough space between components to allow a free flow of air for better heat dissipation.
Provide the maximum possible physical separation between solid state and electromechanical controls. If
possible, the electromechanical controls (motors, starters, solenoids, etc.) should be housed separately or at
the farthest point when enclosed within the cabinet.
We recommend that the EZ7 Series TOUCHPLC have a minimum clear space of 2" on all sides for adequate
ventilation as shown in the image on the left.
Electrical Considerations
This section is designed to provide you with a very basic understanding of electrical noise and how to keep it away
from CPUs. Industrial plants have a number of generators of electrical noise that are sometimes also referred to as
Radio Frequency Interference (RFI). Anytime an inductive load like a motor, motor starter, or solenoid is turned off, it
generates a burst of excess energy that has to flow back to ground, just like electrical energy from a lightning storm
has to flow back to Earth. RFI is short bursts of electrical energy at very high frequencies. Other sources include RF
Welders or Radio Transmitters.
Effect of RFI on Electronic Automation Equipment
Electronic controls use faster and faster CPUs today. These CPUs are also operating at 2.5V to 5VDC logic level power
supply. RFI, if allowed to enter the CPU inside, is a killer of logic. A CPU under this environment loses its brain and
behaves erratically. A smart industrial-grade CPU like the EZ7 Series
TOUCHPLC Card Engine, when faced with RFI, halts its operation instead of
giving false outputs.
Types of RFI
RFI enters electronic controls in two ways: radiated RFI or conducted RFI.
For most practical purposes, electronic devices, unless sitting right next to a
powerful RFI transmitter, will not be affected by noise because air space
severely attenuates such interference. On the other hand, conducted RFI
travels over conductive surfaces such as power supply wires, electrical
wiring of field devices, and worst of all; improper ground planes.
Equipment cabinets usually incorporate one or two doors and/or hinged cabinet panels. Relying on door hinges and
swinging panels for a good metallic bond between hinged parts and the main body of the cabinet does not insure
adequate grounding. Instead, the use of ground straps is recommended. It is vital for the reliable operation of any
electronic device to have any of its metallic surfaces well ground to Earth. This not only provides for safe operation, it
will also drain out any conducted RFI to Earth, away from the CPU's signal ground.
