Esd Guidelines; A.1.2 Esd Guidelines - Siemens SIMATIC TP 270 Operating Instructions Manual

Appendix
A.1 Certificates and Directives
A.1.2

ESD guidelines

What does ESD mean?
Virtually all present-day, electronic modules incorporate highly integrated MOS devices or
components. For technological reasons, these electronic components are very sensitive to
overvoltage and, consequently, to electrostatic discharge. As a result, they are identified as
follows:
• EGB – Elektrostatisch Gefährdeten Bauelemente/Baugruppen
• ESD – Electrostatic Sensitive Devices
The following symbol on plates on cabinets, mounting racks and packages draws attention to
the use of ESD and, thus, to the contact sensitivity of the assemblies concerned:
Figure A-1
ESDs may be destroyed by voltages and energies that are undetectable to a human.
Voltages of this kind occur as soon as a device or an assembly is touched by a person who
is not grounded against static electricity. ESDs exposed to such over voltages may not
immediately be detected as defective. In the majority of cases, faulty
only after a long period of operation.
Precautions against electrostatic discharge
Most plastics are capable of carrying high charges. It is therefore imperative that they be
kept away from ESDs.
When handling electrostatic sensitive devices, make sure that persons, workplaces and
packages are properly grounded.
Handling ESD assemblies
A general rule is that ESDs should be touched only when necessary, for example, when
maintenance is required.
Only touch devices if
• You are grounded by permanently wearing an ESD wrist strap.
• You are wearing ESD shoes or ESD shoe-grounding protection straps in conjunction with
Before you touch an electronic assembly, your body must be discharged. The simplest way
of doing this is to touch a conductive, grounded object immediately beforehand (e.g. bare
metal parts of a cabinet, water pipe etc.).
A-2
Symbol for ESD
an ESD floor.
TP 270, OP 270, MP 270B (WinCC flexible)
Operating Instructions, Edition 03/2004, 6AV6691-1DD01-0AB0
e-establ may occur
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