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Computers primarily use two types of
chips. These include the transistor-transistor logic (TTL) and the
metal oxide semiconductor (MOS). The normal operating level of these chips, in terms
of voltage, is 2.8V, 3.3V, or 5V. Normally, TTL chips run at 5 V and
CMOS chips run at 3.3V or less.
Today, computer components are small and operate at fast
speeds. These characteristics make computer components susceptible
to Electro Static Discharge (ESD). ESD
is the flow of current between two objects with different
electrostatic potentials. For an electrical discharge to be
destructive to a computer, it does not have to release high levels
of energy. ESD can destroy internal components with a relatively
low release of voltages. Most computer components can be damaged or
completely destroyed with a charge between 10 and 20 volts. Humans
cannot feel much below 30 volts of static electricity. Computer
technicians or end users can unknowingly damage the computer. For
this reason, it is important to consider ESD in the workspace. The
best way to protect against ESD is to use precautionary tools and
measures in work areas.
Release static electricity by either touching the metal case or
wearing a wrist strap before contacting any internal components.
However, static electricity can build up while working on the
computer system. To help prevent against the harmful affects of
ESD, touch the metal computer case throughout the troubleshooting
process.
Prevention Measures
ESD is a product of the surrounding environment. ESD is more
likely to develop in a cold, dry environment. A warm, damp
environment will help reduce ESD. Humidifiers can be introduced
into the environment to help provide a damp environment.
Another way to protect against ESD is by using preventive
tools:
- Wrist Straps
– When handling computer components, use a
wrist strap to guard against ESD. An anti-static wrist strap works
by grounding the technician to the component they are working on.
The technician and computer component will have the same
electrical charge and static electricity will not flow between the
two. An anti-static wrist strap must stay in constant contact with
the technician's bare skin.
- Bench and Floor Mats – Bench and floor mats help reduce
static electricity. As the technician is moving around, the floor
mat will drain any static electricity. Floor mats should have a
grounding strap connected to a ground and should be cleaned
frequently for effective prevention of ESD. Also, avoid plastic,
vinyl, carpet, and finished or waxed surfaces in the work area.
- Grounding
– Workbenches should be grounded to dissipate
static electricity. This will help prevent against the damages of
ESD. Also, keep the workbench clear of any coffee, tools, and
stereo equipment.
- Anti-Static Packaging
– Proper handling care should be
taken to protect against ESD. Handle computer parts only at the
edges. If a static release occurs directly with circuitry, the
part might fail. Also, parts should be stored in antistatic bags
or bins to protect against ESD. When removing computer components,
place the parts directly in an anti-static bag.
- Anti-static Sprays – Using anti-static sprays in the
workplace helps reduce static electricity. Apply the anti-static
spray with a soft cloth to the work area.
ESD is very important. Different ways to cope with ESD have
been discussed throughout the previous chapters. ESD was discussed
in Chapter 10, "Preventive Maintenance.
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