Goldanalytix GoldScreenBox Instruction Manual page 15

Important: Always wait 2-3 seconds between measurements, so the GoldScreenBox has time to
autocalibrate. If the coins are placed too quickly, the values might deviate. If you are not sure
whether the measured value is correct, just take the object off the measuring field, wait a few
more seconds, and measure again.
Penetration depth of the GoldScreenBox: Depending on the conductivity of the material, the
GoldScreenBox penetrates differently deep into the precious metals. This is in relation with the
particular procedures during the induction of eddy currents. In case of highly conductive materials
like silver, the penetration will not be as deep as in case of metals of the middle zone (pure gold or
.986 gold) and the low conductivity zone (e.g. Krugerrand alloys at 9.7 MS/m). In case of silver, you
can expect about 250 µm penetration depth, whereas in case of the Krugerrand alloy the
penetration depths is up to 650 µm (0.65 mm). However, this is relatively deep, if you keep in
mind that most gold- or silver-plated layers are only 10 to 60 µm thick. It depends on these
numbers, up to which size the precious metal objects can be measured. Generally speaking, you
can measure 1 kg silver bar with this device - there will be a conductivity value. However, in case
of such big objects, it is very possible that the forgers apply much thicker precious metal layers
around the fake core. Then the GoldScreenBox will not give you a reliable answer. "Smaller"
objects are normally penetrated completely by the magnetic induction field - in case of bigger
ones (from 50 to 100 g, according to their geometry), forgers would have to use very little
amounts of fake material in order to not get caught. It is questionable if this is lucrative for them -
however, it is possible that from this size onwards, there are objects with a deeper core. This is
why you should always use more than one suitable testing method. In case of bigger bars, you
should definitely use ultrasound as well.
Testing objects should exhibit a thickness of at least 1 mm (an exception are the Austrian gold
ducats - see type B in the following conductivity table, for thinner objects see "Special case small
coins and bars.)
Blisters and capsules can have a thickness of up to 3 mm. Not every material shields in the same
manner. If there are metallic components in the supposed plastic package, no reliable or
convincing measurement can be guaranteed. Our test measurements with e.g. NGC packages have
shown that they are too thick because there are several millimeter air gaps between the object
and the packaging. Unfortunately, this kind of package cannot be measured. In this case you have
to either open the package or the objects cannot be measured with the GoldScreenBox.
The striking and the height of the edge (especially in case of coins) can lead to a deviation into the
"orange-red" range, even though it is not a fake. Always put all your objects with the front- and
the backside on the device.
Fine silver coins with a silver content of .9999 (Maple Leaf or Kangaroo) feature a higher
conductivity value than .999 coins. This sensitivity has an influence especially on the mentioned
deep embossings or high edges. That´s why .9999 silver coins and bars, respectively, are in the
range of 62 to 64 MS/m – these values are beyond the set value of silver, but because of the
measurement configuration, this is no reason to be worried about.
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