2
•
Lasting low relative humidity can cause washer contraction and ESD and cause problems
including loose mounting 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, see "
."
Cleanliness
Dust buildup on the chassis might 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 1 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
μ
m
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 2 Harmful gas limits 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 the following ways:
•
A conduction pattern of capacitance coupling.
•
Inductance coupling.
•
Electromagnetic wave radiation.
•
Common impedance (including the grounding system) coupling.
To prevent EMI, use the following guidelines:
•
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.
•
To prevent signal ports from getting damaged by overvoltage or overcurrent caused by lightning
strikes, route interface cables only indoors.
