HP rp3440 Site Preparation Guide, Fifth Edition - HP 9000 rp3410/rp3440 - Page 30

General Site Preparation Guidelines Environmental Elements 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 2-1 Effect of Humidity on ESD Charge Levels Personnel Activitya Humidityb and Charge Levels (voltages)c 26% 32% 40% 50% Person walking across a linoleum floor 6,150V 5,750V 4,625V 3,700V Person walking across a carpeted floor 18,450V 17,250V 13,875V 11,100V Person getting up from a plastic chair 24,600V 23,000V 18,500V 14,800V a. Source: B.A. Unger, Electrostatic Discharge Failures of Semiconductor Devices (Bell Laboratories, 1981). 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. 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 30 Chapter 2