64 ControlEdge HC900 Process & Safety Controller User and Installation Manual Revision 10
May 2019
CE Conformity
Electrical noise produces undesirable effects in measurements and control circuits.
Digital equipment is especially sensitive to the effects of electrical noise. You should use the following
methods to reduce these effects:
Supplementary bonding of the controller enclosure to a local ground, using a No. 12 (4 mm
2
)
copper conductor, is recommended. This may help minimize electrical noise and transients
that may adversely affect the system.
Separate external wiring – group connecting wires into bundles (see Table 5) and route the
individual bundles through separate conduits or metal trays.
Use shielded twisted pair cables for all Analog I/O, Process Variable, RTD, Thermocouple, dc
millivolt, low level signal, 4-20 mA, Digital I/O, and computer interface circuits. Ground
shields as described in the section I/O Module Installation and Wiring page 80.
Use suppression devices for additional noise protection. You may want to add suppression
devices at the external source. Appropriate suppression devices are commercially available.
Refer to document 51-52-05-01 How to Apply Digital Instrumentation in Severe Electrical
Noise Environments for additional installation guidance.
Grouping Wires for Routing
Wires that carry relatively high electrical energy can produce unwanted noise in wires that transmit
signals of relatively low energy, particularly when they are placed parallel in long wiring runs. Collect
and bundle wires of similar type, and route the bundle separate from bundles of other types. Table 6
provides suggested guidelines for grouping wires.
Table 5 – Guidelines for Grouping Wires
Analog signal wire, such as:
Input signal wire (thermocouple, 4 mA to 20 mA, etc.)
4-20 mA output signal wiring
Slidewire feedback circuit wiring
Communications
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