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It is also possible to phase out a particular size of non-ferrous contaminant but be able to detect a
smaller or larger size. This is because the metal signal matches the product signal and has been
compensated out.
It is important to be aware of the effects of contaminant orientation and relative detectability. The test
wands used throughout the metal detection industry are spherical, as this eliminates any orientation
effects and ensures repeatability. However, in practice this may not always be the case, therefore the
user must be mindful of this fact.
Regular In-Line Detector Performance Testing
It is important to maintain regular and accurate in-line performance testing of the metal detector using
the same techniques as the initial performance testing. This should include tests to ensure that the
reject systems are effective. See
Regular testing should be conducted using the same techniques as initial performance testing. This
should include ensuring that the reject systems are effective, including reject confirmation systems if
fitted.
The records generated by this system should be maintained in a safe and easily retrievable place for
a time period suited to your particular quality regime. Factors which may be of help in determining a
suitable retention period might be:
The anticipated life of your product within normal consumer usage.
Any statutory time period within which enforcement authorities may instigate legal
proceedings after notification of a complaint.
Handling Rejected Products
A reject collection device, such as a reject bin, will typically be used to prevent contaminating
products from being mixed with uncontaminated products. Any rejected product should be kept
segregated for later examination. Never let your bin overfill.
It is advisable to examine rejected product with a view to identifying any contamination.
The information gained can be used to implement preventative measures, thus improving further the
product. Multiple contaminants may be a clue to machinery break-up. Identification can then pinpoint
the source and effective maintenance can then be conducted.
3
The IQ
+ ST Metal Detector can also be helpful when examining contaminated products. For
example, you can alter the orientation of the product and pass it back through the metal detector to
help identify its position. Alternatively, you can subdivide a large product into a number of smaller
samples and then use the metal detector to identify which sample contains the contaminant.
Getting the Results
Before using the metal detector with a new product it is important to learn the product, to allow the
metal detector to adjust itself to the highest possible sensitivity.
The metal detector will either learn on the signal from the product, or if there is insufficient signal, will
use reference learn settings. This reference signal is chosen to maximise the sensitivity of the metal
detector, so it is always preferable. However, where a product generates a signal in the detector,
referred to as product effect, then the detector must learn this signal instead (otherwise good product
will falsely be rejected).
When there is no signal from the product this is because they are non-conductive in nature, usually
because they are dry (low water content) such as tea and coffee. Frozen products are also dry in
nature because water cannot conduct when it is frozen. During a product learn, the detector will
automatically sense if it is possible to run dry (use the reference learn setting), but this can also be
forced by selecting DRY YES in the product menu.
Using Performance Validation
Using the Metal Detector
for further details.
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