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The art (or is it science?) of grounding
personnel at ESD safe workstations is much more developed
than even I realized before my interview with Bette Palmisano
of Work Surfaces Corporation. Ms Palmisano says that the use
of top quality hardware allows a very reliable grounding system
with less chances for breakage or disconnects.
At an ESD safe workstation personal must
use wrist straps to ensure they are grounded and therefore
drain or dissipate static charges which could wreck ESD sensitive
items. These wrist straps usually have a 1 Meg Ohm resistor
in their connector or wiring which protects the wearer from
hazardous electrical potentials. The connection of the workbench
and ground is usually through a "banana" plug or "alligator
" clip.
Work Surfaces Corporation as well as other
companies supply a variety of sophisticated connection hardware
to provide reliable grounding means for personnel and workbenches.
One major problem encountered by wrist strap
users is the stress placed on the connection and wiring during
normal use. This stress placed on the wire and plug of the
wrist strap as the user moves around eventually will cause
a break and loss of grounding. This renders the wrist strap
inoperative. Most companies require wrist strap users to check
the wrist strap before beginning work each day. Some require
the user to check the connection each time they return to
their work area after break, lunch etc. Many companies use
continuous monitors on the wrist strap connection. If a wrist
strap wire or connector breaks between operational checks,
all parts handled since the last check are suspect and probably
should be tested if not discarded.
Work Surfaces Corporation has developed a
unique connector system to help eliminate the problem of stress
on the wiring and connector. They have a neat 360 degree swivel
connector that moves with the user as they perform their job
tasks. (picture swivet in desk with wrist band only)
We tested the connector over an extended
period of time and found it worked flawlessly. In fact we
saw no change in resistance during our entire test. The resistance
varied between 0.1 Ohms and 0.2 Ohms. We looked at the connection
with an oscilloscope while the connection was loaded with
a small amount of electrical current Ð about 10 mA. We saw
virtually no "scratchiness" in the signal -<0.01 nV. This
is a good test for the integrity of the connection under use
or as it swiveled. We found the swivel connector to be highly
functional and exceptionally reliable.
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