Loma IQ3+, Руководство пользователя

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Using the Metal Detector
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Based on this product effect , the metal detector automatically makes the required settings in the
software and establishes a product window or envelope which is saved in memory for use every time
the product is selected for inspection.
The product effect is then effectively filtered out from the signal received when being inspected so that
signal variations caused by metal contaminants can be easily detected.
Carrying out a full product learn process is therefore a very important first step to ensure that the
metal detector performs effectively.
Establishing Detector Performance
Once the metal detector has been set up with the product it is important to establish what size of
metal contaminant the detector is capable of finding and if necessary make manual adjustments in the
metal detector settings to achieve the required results.
This is achieved by attaching various sizes and types of metal to know good product samples and
passing them through the metal detector aperture to establish the level of detection that is achievable.
Loma Systems can supply a selection of sizes and types of metal test wands for attaching to product
samples for testing purposes. There are three types of wands: ferrous (chrome steel), non-ferrous
(brass), and 304 stainless steel. Stainless steel is included because performance is generally poorer
than for other non-ferrous contamination due to the relative conductivity of the material. The wands
are supplied in a range of sizes depending on the product type being inspected.
In dry running the performance can be measured by placing the test wand at the trailing and leading
edges of a representative sample of the product, and then passing the product through the detector.
The test wands should be placed at the leading and trailing edges of the product to ensure correct
product rejection. This is particularly important in metal detectors with no Product Registration Photo-
eye fitted, as the reject time is determined by the position of the contaminant relative to the product.
With conductive products the signal generated by the metal contaminant can be masked by the
product itself. It is therefore important to test the product with test wands not only at the leading and
trailing edges, but also at the product‘s centre.
Relative Detectability of Non-Ferrous Metals
The resistance, and hence ease of detection, of different non-ferrous metals varies widely. The more
conductive they are, the easier they are to detect, as shown in the graph below.
Performance for stainless steels is invariably poorer than to other non-ferrous contamination. This is
largely due to the relative conductivity of the material.