Sartorius MC 210 S, Инструкция по установке и эксплуатации, Страница: 20 / 188

General Instructions for
“Analytical Weighing”
Weighing Electrostatically Charged Samples
and Containers
Major measuring errors can occur when
electrostatically charged samples and containers are
weighed. This problem particularly involves samples
that have an extremely poor electrical conductivity
(glass, plastic, filters) since they can discharge
electrostatic – i.e., friction-induced – charges only
over a relatively long period of time. The result
is an interaction of forces among the charges
adhering to the sample and the stationary components
of the balance (base plate of the weighing chamber,
draft shield construction, balance housing). This
is noticeable when the weight readout drifts. At a
high humidity, this effect is not so pronounced or does
not even occur at all due to the thin layer of water that
condenses on the sample and, through conductive
discharge, counteracts interfering static electricity.
In addition to taking purely mechanical counteractive
measures (protecting the sample using a special
antistatic weighing pan – see the “Accessories”), you
can neutralize the surface charges by “bombarding”
them with ions of the opposite polarity. This
is an extremely effective method of eliminating static
electricity on surfaces (antistatic ionizing blower,
order no. YIB01).
The balance’s environment, including the operator,
can considerably interfere with weighing on account
of static electricity. The balances of the MC Series
have been designed to counteract this phenomenon:
the glass surfaces of the draft shield have a special
metallic coating.
The rear panel of the balance/weighing cell
has a terminal
(15)
for connecting an equipotential
grounding conductor. It is used for additionally
grounding a peripheral device (for example,
a vibrating spatula). This terminal is designed for
single grounding wires up to .25” standard gauge
or 6 mm
2
and for .18” standard gauge or 4 mm
2
stranded wires.
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