9
Electrostatic discharge (ESD)
Electrostatic discharge is a sudden current flowing from a charged object to another
object or to ground. Electrostatic charges can accumulate on common items such as
foam drinking cups, cellophane tape, synthetic clothing, untreated foam packaging
material, and untreated plastic bags and work folders, to name only a few.
Electronic components and assemblies, if not properly protected against ESD, can be
permanently damaged or destroyed when near or in contact with electrostatically
charged objects. When you handle components or assemblies that are not in protective
bags and you are not sure whether they are static-sensitive, assume that they are static sensitive
and handle them accordingly.
• Perform all service procedures in a static-protected environment. Always use
techniques and equipment designed to protect personnel and equipment from
electrostatic discharge.
• Remove static-sensitive components and assemblies from their static-shielding bags
only at static-safe workstations—a properly grounded table and grounded floor mat—
and only when you are wearing a grounded wrist strap (with a resistor of at least 1
megaohm in series) or other grounding device.
• Use only grounded tools when inserting, adjusting, or removing static-sensitive
components and assemblies.
• Remove or insert static-sensitive components and assemblies only with monitor
power turned off.
• Insert and seal static-sensitive components and assemblies into their original static shielding
bags before removing them from static-protected areas.
• Always test your ground strap, bench mat, conductive work surface, and ground
cord before removing components and assemblies from their protective bags and
before beginning any disassembly or assembly procedures.
Overview
Purpose and scope
This service manual is a reference for periodic preventive maintenance and corrective service procedures
for the Welch Allyn Pediatric Scales. It is intended for use only by trained and qualified service personnel.
Corrective service is supported to the level of field-replaceable units. These include circuit-board
assemblies and some subassemblies, and other parts.
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