Electrostatic discharge (esd) prevention, Static protection measures, Acoustics – HP 9000 rp5400 Servers User Manual
Page 152: Facility characteristics, Floor loading, Effect of humidity on esd charge levels
Electrostatic Discharge (ESD) Prevention
Static charges (voltage levels) occur when objects are separated or rubbed together. The voltage
level of a static charge is determined by the following factors:
•
Types of materials
•
Relative humidity
•
Rate of change or separation
Table C-1 Effect of Humidity on ESD Charge Levels
Humidity
2
and Charge Levels (voltages)
3
Personnel Activity
1
50%
40%
32%
26%
3,700 V
4,625 V
5,750 V
6,150 V
Person walking across a linoleum floor
11,100 V
13,875 V
17,250 V
18,450 V
Person walking across a carpeted floor
14,800 V
18,500 V
23,000 V
24,600 V
Person getting up from a plastic chair
1
Source: B.A. Unger, Electrostatic Discharge Failures of Semiconductor Devices (Bell Laboratories, 1981)
2
For the same relative humidity level, a high rate of airflow produces higher static charges than a low airflow rate.
3
Some data in this table has been extrapolated.
Static Protection Measures
Follow these precautions to minimize possible ESD-induced failures in the computer room:
•
Maintain recommended humidity level and airflow rates in the computer room.
•
Install conductive flooring (conductive adhesive must be used when laying tiles).
•
Use conductive wax if waxed floors are necessary.
•
Ensure that all equipment and flooring are properly grounded and are at the same ground
potential.
•
Use conductive tables and chairs.
•
Use a grounded wrist strap (or other grounding method) when handling circuit boards.
•
Store spare electronic modules in antistatic containers.
Acoustics
Computer equipment and air conditioning blowers cause computer rooms to be noisy. Ambient
noise level in a computer room can be reduced as follows:
•
Dropped ceiling—Cover with a commercial grade of fire-resistant, acoustic rated, fiberglass
ceiling tile.
•
Sound deadening—Cover the walls with curtains or other sound deadening material.
•
Removable partitions—Use foam rubber models for most effectiveness.
Facility Characteristics
This section contains information about facility characteristics that must be considered for the
installation or operation of an hp server. Facility characteristics are:
•
Floor loading
•
Windows
•
Altitude effects
Floor Loading
The computer room floor must be able to support the total weight of the installed hp server as
well as the weight of the individual cabinets as they are moved into position.
Floor loading is usually not an issue in nonraised floor installations. The information presented
in this section is directed toward raised floor installations.
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General Site Preparation Guidelines