Hardware Reference
In-Depth Information
Preventing Electrical Damage
Computers run on electricity, but they're pretty specifi c about the amount and type they
need. The wrong type of electricity can weaken and even destroy a circuit board or processor
chip. Here are some electrical threats about which you should be aware.
Electrostatic Discharge
Electrostatic discharge
(
ESD
) is the most common culprit for ruined PC parts, although
many people have never heard of it. ESD is really just static electricity, the same thing that
can shock a person on a low-humidity day.
ESD occurs when two items of unequal voltage potential come into contact with one
another. The item with the higher charge passes electricity to the one with the lower charge
to even out the voltage. As an analogy, picture two bodies of water meeting; if one has a
higher level, water will fl ow quickly into the other one until they're the same. In the case of
electricity, the equalization happens so fast that the item of lower charge receives a rush
of electricity that feels like a shock. You've experienced ESD fi rsthand if you've ever
scuffed your socks on the carpet and then touched someone, giving the person a shock.
You were not shocked yourself because, in that case,
you
were the item of higher charge.
Whereas voltage (measured in volts) is the difference in electrical charge,
current
is the rate
at which electrical charge fl ows and is measure in
amps
. ESD is a high-voltage shock (3,000
volts or so), but it doesn't harm a person because it has very low current. The human body
doesn't draw electricity very strongly; it merely draws enough to equalize the charge and then
stops. To damage a human body, there must be suffi cient amps as well as volts. That is why a
110-volt wall outlet can hurt a person more than a 3,000-volt static electricity shock.
Electronic equipment, though, is extremely sensitive to damage by high voltage, even
when the amperage is very low. Humans notice ESD only when it reaches 3,000 volts or
so, but ESD can damage a circuit board with less than 1 percent of that. (Some experts say
as little as one volt is enough to do some damage.) This means that a person could touch
a circuit board and destroy it with static electricity without even noticing. The next time
they tried to use that circuit board it would be dead, and they would have no idea why.
Furthermore, ESD damage doesn't always show up immediately. It may cause the device to
malfunction, or it may weaken the device to the point that it fails a week or a month later.
Generally speaking, any exposed circuit boards are targets for ESD damage, especially
motherboards. Also at risk are microchips both on and off those boards, particularly RAM
and ROM. Devices
not
very susceptible to ESD damage include those in which circuit
boards are never exposed, such as keyboards, mice, speakers, monitors, and printers, and
those that don't contain circuit boards.
If you never open your computer's case, the risks of harming it via ESD are very low. If
you have to work inside a computer for some reason, such as to install a new circuit board
or more RAM, here are some tips:
Be aware of the clothing you wear when working inside a PC. Synthetic materials such
as nylon generate much more ESD than natural fi bers like cotton and wool, so dress
in natural fabrics. Avoid working in stocking feet—wear rubber-soled shoes. Keeping
the humidity high in the work area can also help considerably. The ideal humidity for
working on PC hardware is 50 to 80 percent.
