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Operation of the Magne-Gage is based on the magnetic attraction between a small selected
permanent magnet and the substrate or the coating of the materiel being tested. The
Magne-Gage is essentially a sensitive spring balance, indicating on it's graduated dial
the degree of force required to detach it's permanent magnet from the surface of the
specimen.
As a non magnetic coating, or a coating of a lesser magnetic permeability ( such as
nickel) is interposed between the steel or iron base and the permanent magnet, the
attractive force is diminished, decreasing as the thickness of the coating is increased.
When nickel and other ferro-magnetic materials are coated on a non-magnetic base metal or
plastic, the force required to detach the magnet increases with an increase of coating
thickness.
Nickel and other ferro-magnetic coatings can be measured on magnetic base metals, in as
much as they display lesser attractive force than the iron or steel base, and therefore
diminish in the force to detach with an increase of thickness.
Seven calibrations are available for measurement of types I and II platings and coatings
of varying thickness'.
To
measure a coating thickness, the operator brings the Magne-Gage magnet into contact with
the specimen surface and turns the dial knob until the magnet pulls free from the
specimen. At this point, the dial reading is noted and, when referred to a calibration
curve, gives a thickness measurement.
No electrical circuits are involved; no special skills or training is required. Before
shipping, every Magne-Gage is calibrated with master thickness standards prepared and
certified by the National Institute of
Standards and Technology (N.I.S.T.).
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