Appendix
A.1 Certificates and Directives
TP 270, OP 270, MP 270B (WinCC flexible)
A-2 Operating Instructions, Edition 03/2004, 6AV6691-1DD01-0AB0
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 Symbol for ESD
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
!
e-establ may occur
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
an ESD floor.
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.).
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