HP L1000 - 9000 - 0 MB RAM, User Manual

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Appendix C
General Site Preparation Guidelines
Environmental Elements
202
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
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.
Table C-1 Effect of Humidity on ESD Charge Levels
Personnel Activity
a
a. Source: B.A. Unger, Electrostatic Discharge Failures of Semiconductor Devices
(Bell Laboratories, 1981)
Humidity
b
and Charge Levels (voltages)
c
b. For the same relative humidity level, a high rate of airflow produces higher
static charges than a low airflow rate.
c. Some data in this table has been extrapolated.
26% 32% 40% 50%
Person walking across a
linoleum floor
6,150 V 5,750 V 4,625 V 3,700 V
Person walking across a carpeted
floor 18,450 V 17,250 V 13,875 V 11,100 V
Person getting up from a plastic
chair 24,600 V 23,000 V 18,500 V 14,800 V