8
• Lasting high relative humidity can cause poor insulation, electricity creepage, mechanical property
change of materials, and metal corrosion.
• Lasting low relative humidity can cause washer contraction and ESD and bring problems including
loose captive screws and circuit failure.
• High temperature can accelerate the aging of insulation materials and significantly lower the
reliability and lifespan of the switch.
For the temperature and humidity requirements of different switch models, see "Appendix A Technical
spec
ifications."
Cleanness
Dust buildup on the chassis may result in electrostatic adsorption, which causes poor contact of metal
components and contact points, especially when indoor relative humidity is low. In the worst case,
electrostatic adsorption can cause communication failure.
Table 2 Dust concentration limit in the equipment room
Substance Concentration limit (particles/m³)
Dust
≤ 3 x 10
4
(no visible dust on the tabletop over three days)
NOTE:
Dust diameter ≥ 5 μm
The equipment room must also meet strict limits on salts, acids, and sulfides to eliminate corrosion and
premature aging of components, as shown in Table 3.
Table 3 Harmful gas li
mits in the equipment room
Gas Maximum concentration (mg/m
3
)
SO
2
0.2
H
2
S 0.006
NH
3
0.05
Cl
2
0.01
EMI
All electromagnetic interference (EMI) sources, from outside or inside of the switch and application
system, adversely affect the switch in a conduction pattern of capacitance coupling, inductance coupling,
electromagnetic wave radiation, or common impedance (including the grounding system) coupling. To
prevent EMI, take the following actions:
• If AC power is used, use a single-phase three-wire power receptacle with protection earth (PE) to
filter interference from the power grid.
• Keep the switch far away from radio transmitting stations, radar stations, and high-frequency
devices.
• Use electromagnetic shielding, for example, shielded interface cables, when necessary.
• Route interface cables only indoors to prevent signal ports from getting damaged by overvoltage or
overcurrent caused by lightning strikes.
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