Siemens SIMATIC Panel PC 870 Equipment Manual page 144

ESD Guidelines
Avoid direct contact
As a general principle, only touch electrostatic sensitive devices when this is
unavoidable (e.g. during maintenance work). To prevent discharge energy from
reaching and damaging sensitive components, hold the components in such a
way that you do not touch the pins or the printed conductors.
If you have to perform measurements on an assembly, discharge your body by
touching a grounded metallic object before carrying out the work. Use only
grounded measuring instruments.
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SIMATIC Panel PC 870 Computing Unit, Equipment Manual
Release 11/02