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Danaher Motion
The two different methods of terminating shields are used to accommodate two
different immunity requirements. Immunity required inside an enclosure is considered
lower because cables are typically less than 3 meters in length and/or can be
separated from each other and from noise sources.
Immunity required external to an enclosure is considered higher because the user
may have less control over the noise environment. Low level signal cables that can be
external to an enclosure and AC/DC digital I/O cables have been tested at a 2 KV
level for electrical fast transients (EFTs). Low level signals that can be less than 3
meters in length or can be separated from noise sources are tested at a 1 KV level.
Under the stated conditions, there will be no disturbance of digital I/O, encoder, or
stepper operation. For analog signals, there may be momentary disturbances but
there will be self-recovery when the noise subsides.
In order to meet the EU directive requirement for emissions and immunity, fiber optics
must be used for I/O expansion.
Although the control will pass the electrical fast transient test on incoming power lines,
users may still want to use a power line conditioner.
As a general precaution, do not operate transmitters, arc welding equipment, or other
high noise radiators within one meter of a PiC enclosure that has the door open.
Continue to equip inductive devices, if they are in series with a mechanical contact or
switch, with arc suppression circuits. These devices include contactors, solenoids and
motors. Shield all cables that carry heavy current near the system, using continuous
foil wrap or conduit grounded at both ends. Such cables include power leads for high-
frequency welders and for pulse-width-modulated motor drives.
Shields for signal wires are grounded at only one end, to provide immunity to
outside noise sources. However, the shields for "noise sources" are ground-
ed at both ends, to reduce emissions and "contain" the noise.
Worst case tests with analog I/O modules have caused momentary disturbances no
greater than .5V in a +10V to -10V range and .5 mA in a 4 to 20 mA range. Worst case
tests with an RTD module have caused momentary disturbances no greater that + or -
Standalone MMC Hardware Manual
version 15.1
Figure 11-3: Connecting Shielded Cable
MMC
Module
CE and EMC Guidelines
External
Device
Cabinet
Enclosure
NOTE
165
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