Rockwell Automation 2080-LC50 Micro830 and Micro850 Programmable Controllers User Manual - Manual (Page 51)

Rockwell Automation Publication 2080-UM002F-EN-E - December 2013 37
Wire Your Controller Chapter 4
Minimize Electrical Noise
Because of the variety of applications and environments where controllers are
installed and operating, it is impossible to ensure that all environmental noise will
be removed by input filters. To help reduce the effects of environmental noise,
install the Micro800 system in a properly rated (for example, NEMA) enclosure.
Make sure that the Micro800 system is properly grounded.
A system may malfunction due to a change in the operating environment after a
period of time. We recommend periodically checking system operation,
particularly when new machinery or other noise sources are installed near the
Micro800 system.
Analog Channel Wiring Guidelines
Consider the following when wiring your analog channels:
• The analog common (COM) is not electrically isolated from the system,
and is connected to the power supply common.
• Analog channels are not isolated from each other.
• Use Belden cable #8761, or equivalent, shielded wire.
• Under normal conditions, the drain wire (shield) should be connected to
the metal mounting panel (earth ground). Keep the shield connection to
earth ground as short as possible.
• To ensure optimum accuracy for voltage type inputs, limit overall cable
impedance by keeping all analog cables as short as possible. Locate the I/O
system as close to your voltage type sensors or actuators as possible.
Minimize Electrical Noise on Analog Channels
Inputs on analog channels employ digital high-frequency filters that significantly
reduce the effects of electrical noise on input signals. However, because of the
variety of applications and environments where analog controllers are installed
and operated, it is impossible to ensure that all environmental noise will be
removed by the input filters.
Several specific steps can be taken to help reduce the effects of environmental
noise on analog signals:
• install the Micro800 system in a properly rated enclosure, for example,
NEMA. Make sure that the shield is properly grounded.
• use Belden cable #8761 for wiring the analog channels, making sure that
the drain wire and foil shield are properly earth grounded.
• route the Belden cable separately from any AC wiring. Additional noise
immunity can be obtained by routing the cables in grounded conduit.