Datalogic GRYPHON ESD D200 Snelle referentie - Pagina 15
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ESD INFORMATION
What is ESD?
ESD stands for ElectroStatic Discharge.
Static electricity is an everyday phenomenon - there can be few
of us who have not experienced a static shock on getting out of
a car or after walking across a room and touching the door
knob.
Other examples of static electricity are the cling of some fabrics
to the body, the sticking of a plastic document cover, or the
attraction of dust to a TV or computer screen. It can build up
rapidly on objects, to produce surprisingly high voltages.
Static electricity occurs when an object has an imbalance in its
electric charge. Objects with excessive electrons carry a
negative charge, whereas objects lacking electrons carry a
positive charge. Charged objects need to be neutralized to
remedy this unstable energy state. If two objects that have
different voltages approach each other closely enough, charge
may pass from one object to the other in a fast electrostatic
discharge. While this only lasts a microsecond or less, the peak
discharge current can be several Amps and the peak power
can be in the kiloWatt range! This discharge of electrons is
called ESD. ESD occurs when the resistance provided by the
air gap is less than that of other available paths to ground.
Why worry about ESD?
Basically because it can damage electronic components and
circuits.
We usually feel ESD, but ESD happens also at lower levels
that we cannot feel. Many ESD events are well below the
human sensitivity threshold of 3000 V but, unfortunately, an
increasing number of electronic components are susceptible to
damage from increasingly lower voltage levels. This trend will
continue as consumers demand more-compact products, with
increasing circuit density and decreasing component size.
Event levels as low as 20 V can damage some of the more
sensitive components.
ESD can cause unseen damage to electronic components
during manufacture of electronic assemblies and equipment. If
the damaged component fails immediately, the result can be a
board that fails tests and requires rework. This represents lost
production and additional manufacturing costs.
Worse than this, a component may be partially damaged and
weakened. It may suffer a change or drift in characteristics. It
may remain within specification, but fail later when in use by a
customer. This is the most expensive type of failure, as it can
cause:
•
Customer dissatisfaction
•
Customer service personnel and facility cost
•
Engineers time, possibly for on-site repair with travel, and
parts replacement