Thermo Scientific APEX 100 User Manual page 260

Recommended Test Procedures
You should thoroughly test the detector and all reject devices when these are first
installed, and whenever a major component of the system is changed or altered—for
example, when any part is serviced or repaired. In addition, when setting up the test
procedures for your particular working environment, please take note of the following
considerations and recommendations.
Pass Test Samples Through the Center of the Search Head
The least sensitive part of the search head is along the centerline of the opening. As a
result, it is best run test sample passes through the centerline of the opening. If the test
sample is run at the side of the aperture or product tube, this will produce a larger signal
than through the centerline. The test procedure should consider this for consistent
results.
Choose Appropriately-Sized Test Samples
Sensitivity capabilities of different detectors used in different applications will vary.
Smaller aperture is capable of detecting smaller pieces of metal. Product effect may also
alter the detection capability. It is inadvisable to rely on a corporate standard to
determine and test the detector's operation. Ideally, each detector should have its own
standards of operation and a corporate outline should be used only as a maximum
allowable guide. Sample sizes should be selected so that they are clearly detectable
when compared to the signal produced by the product or other interfering signals. If
samples are established which are very close to the product signal, frustration on the
part of operators can lead to a lack of confidence in the detector's operation.
Use the Normal Product Flow-Rate During Testing
The detector should be tested at its normal operating speed. Test samples should be
placed on conveyors so that they will pass through the detector at normal speed. On
pipelines, test samples should be inserted so that they travel through the search-head at
the product's normal flow. On gravity-feed and tablet/pharmaceutical applications, test
samples should be placed so they fall from same point as the product.
Ferrous Metals Are Easier to Detect than Stainless Steel
The detector is not equally sensitive to all types of metal. Depending on the type of
product and application there can be three typical metal groups which will produce three
different levels of detection. Ferrous metals are the easiest to detect, and non-magnetic
stainless steels are the most difficult to detect.
• Ferrous metals—any iron derivative.
• Non-ferrous metals—any good electricity-conducting metals such as aluminum,
copper, brass, and so forth.
• Stainless steel—any of the 300-series stainless steels, which are non-magnetic.
These are often the most difficult metals to detect.
Page 260 Thermo Scientific APEX User's Guide