NSG 438
4
3
Introduction
Under appropriate ambient conditions, both material objects and even the
human body itself can become charged with electrical energy. This effect
is due to "electrostatics", a phenomenon that has been known since the
earliest times. Thales von Milet (600 BC) noticed how amber attracted very
light particles when it was rubbed. Touching a charged item against a
conductive object leads to a charge equalization through a spark
discharge, which produces a brief but powerful electro-magnetic field.
3.1.
Electrostatic discharge (ESD*)
This effect can be explained as follows: Two insulating substances with
differing dielectric constants become charged when rubbed together, i.e.
one material gives electrons to the other one. This effect is known as
electrostatic charging. The same can happen to a person. When
somebody walks around in a dry atmosphere on carpet while wearing
shoes with good insulating properties, a charge of several thousand volts
can be built up. If, now, that person comes close to a conductive surface,
the charge that he or she is carrying flows away through a hefty spark
discharge.
The high equalizing current that flows, and the associated large
electromagnetic field that hence results, can cause electronic devices
(computers, terminals, process controllers, vehicle electronics, solid state
devices, credit or memory cards, etc.) to malfunction or even be destroyed.
* ESD = electrostatic discharge
3.2.
Simulation
A systematic investigation of electronic equipment and installations to
determine their electromagnetic compatibility (EMC) is, today, a necessity
if one is not prepared to suffer the economic disadvantages that could
otherwise ensue. As a logical consequence, appropriate testing is now a
legal requirement for the sale of electronic products within the EU.
The ESD-test plays an important role in the range of interference
sensitivity tests. It simulates frequently occurring effects and guides the
development engineer to any weak spots in an instrument or item of
equipment through a combination of high voltage and high frequency
properties.
