Loma IQ3+, User Manual

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About Metal Detection
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Detector performance is also affected by the position of the contaminant in the aperture. The least
sensitive point is located in the geometric centre of the aperture, so this ideally is where to test the
detector performance each time if practical, to ensure consistency. As metal gets closer to the sides
(coils) of the aperture, the signal generated becomes larger, making it easier to detect.
Types of Metal
Metal detector performance is not the same for all types of metal. The ease of detection depends on
how easily they are magnetised, the magnetic permeability, and the electrical conductivity of the
metal. Metal detectors are calibrated for optimum detection performance of ferrous metals, non-
ferrous metals and stainless steel.
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Ferrous
Ferrous materials are any metal that is easily attracted to a magnet, such as steel and iron.
Typically ferrous metals are easiest to detect and usually the most common contaminant
outside of food processing plants.
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Non-Ferrous
Non-ferrous materials are highly conductive, non-magnetic metals such as copper, aluminium,
brass and phosphor bronze. When inspecting non-conductive products, these metals produce
almost the same size signal as ferrous metals because they are all good conductors. When
inspecting conductive products, increasing the test sphere size by at least 50% is a good
practice.
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Non-Magnetic Stainless Steel
High quality 300 series stainless steels, such as types 304 and 316, are the most difficult metals
to detect due to their poor electrical conductive qualities and low magnetic permeability. These
are commonly used in the food processing and pharmaceutical industries.
When inspecting non-conductive products, a stainless steel test sphere typically needs to be
50% larger than a ferrous sphere to produce the same size signal. When inspecting conductive
products, a stainless steel test sphere needs to be 200% to 300% larger than a ferrous sphere
to produce the same size signal.
When detection specifications include non-ferrous and/or stainless steel, the particular metals
and sizes should be identified. Correct identification of what particles should be detected is
critical because these metals have many varieties and they will all look slightly different to the
metal detector.
Shapes and Orientation of Metal
Metal detector standards are based on testing using sphere shaped pieces of different types of metal
and in different sizes. This is because spheres are the same shape and size when viewed from any
angle.