1. INTRODUCTION AND MODE SELECTION
1.1 PURPOSE
The Sencon SI9500 Digital Film Weight Gauge is an instrument designed for
use in the can, end and lid making industries. It enables the film weight of
lacquers and coating to be measured.
By incorporating a microprocessor and advanced electronic techniques into
the instrument it has been made capable of optimum accuracy, linearity and
ease of use.
1.2 METHOD OF MEASUREMENT
The instrument establishes film weight by measuring the capacitance
between a conductive probe tip and the metallic substrate whilst separated
only by the lacquer film under test.
The capacitance will be proportional to the separation between probe and
substrate (i.e. lacquer thickness) if the probe tip dimensions and dielectric
strength of the lacquer are constant. Unfortunately different formulations of
lacquer exhibit different dielectric strengths, it is therefore necessary to use
the instrument as a comparator to establish film thickness (or weight) of an
unknown sample by comparing it to a known sample of the same lacquer
type.
It should be noted that the electrical signals applied to the probe and the
connection that attaches to the substrate are of low voltage and represent no
hazard whatsoever regardless of how they are handled.
Rubber
tip
Metal
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