Special Case Small Coins And Bars - Goldanalytix GoldScreenBox Instruction Manual

10.

Special case small coins and bars

General
A measuring unit with a clearly defined diameter is built into the GoldScreenBox below the
measuring surface. For material-specific measurements, this result in the necessity that the spread
or the diameter of the objects placed on its surface must correspond approximately to the size of
the measuring unit. However, there is no clear dividing line, since slightly different behavior can
occur depending on the geometry of the object (rectangular bar or round coin). Nevertheless, it
can be stated that gold bars above 5 g and coins from around 4-6 g (e.g. German Empire coins 10
marks, Vreneli 20 CHF etc.) can be measured with the material-specific values.
But what about smaller objects such as 1/10 ounce gold coins or 1, 2, 2.5 or 5 gram gold bars? Can
these also be easily determined and examined on the GoldScreenBox? The answer is yes - albeit
with a few noteworthy restrictions.
Measurement of small coins
Let us explain the facts of the matter with a simple example - we want to measure both, a 1 ounce
Philharmonic Gold 9999 coin and its little sister, the 1/10 ounce Philharmonic.
The following table shows the relevant characteristics of these two embossings:
Name & Size
Philharmonic 1 Oz
Philharmonic 1/10 Oz
When we place the 1-ounce coin on the 20 mm wide measuring circle of the Goldscreenbox, we
obtain almost the standard reference conductance of pure gold at 20 °C [45.0 MS/m]. This is
logical, as the 37 mm wide coin covers the measuring circle completely. How does the 16 mm wide
1/10 ounce coin behave? Here we get a value of about 41 MS/m! How can this be? In both cases it
is pure gold!
The explanation is quite simple: Since the measuring circle is not completely covered, in addition
to the gold content on the covered surface, measurements are also made against air of the
uncovered surface to a certain extent (see figure on next page). This of course means that the
pure conductance of the precious metal is no longer achieved, but a slightly lower one.
It is crucial that the coin or bar is absolutely centred and always placed directly on the measuring
surface. Hereinafter, you will find information about the measurement and the special features of
1/10 coins.
Fineness
Weight
[‰]
999.9 31.10 g
999.9 3.121 g
Diameter Thickness
37 mm 2 mm
16 mm 1.2 mm
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