There are four noise susceptibility levels for cables. Noise susceptibility indicates how well the signal circuit can differentiate
between undesirable noise and the required signal. For example, data communication cables such as RS-232E, RS485, Ethernet,
and xDSL have a higher noise susceptibility than power cables. In general, for a given cable the susceptibility levels are
reciprocal to the radiated emissions levels.
The four noise susceptibility levels are:
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Level 1 (high): Analog signals less than 50 V and digital signals less than 15 V (data communication cables fall into this category). |
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Level 2 (medium): Analog signals greater than 50 V and switching circuits. |
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Level 3 (low): Switching signals greater than 50 V and analog signals greater than 50 V. Currents less than 20 A are also included in this
category. |
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Level 4 (power): Voltages in the range of 0–1000 V and currents in the range of 20–800 A (applies to both AC and DC circuits). |
All permanently installed cables associated with the system must be supported and protected along their entire lengths using
conduits and/or cable trays. Electrical conduits are tubes used to protect and route electrical wiring. Cable trays are used to support insulated electric cables used
for power distribution and communication. They must be manufactured from metal and be firmly grounded with complete electrical
continuity throughout the length of the tray. The trays should also be fully covered to provide adequate shielding.
The separation distance required between a cable with high susceptibility and another cable with varying susceptibility will
vary depending on how your cables are installed:
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Cables contained in separate trays
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Level 1 to Level 2 – 30 mm |
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Level 1 to Level 3 – 160 mm |
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Level 1 to Level 4 – 670 mm |
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One cable contained in a tray and the other in a conduit
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Level 1 to Level 2 – 30 mm |
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Level 1 to Level 3 – 110 mm |
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Level 1 to Level 4 – 460 mm |
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Cables contained in separate conduits
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Level 1 to Level 2 – 30 mm |
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Level 1 to Level 3 – 80 mm |
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Level 1 to Level 4 – 310 mm. |
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