Instrumentation & Measurement Magazine 23-2 - 89

Fig. 1. Typical examples of coins used as measure of size. (a) Fig. 2, from [11]
(©2016 IEEE), (b) Fig. 2, from [12] (©2016 IEEE), (c) Fig. 3, from [13] ©2016
IEEE) and (d) Fig. 4a, from [14] (©2016 IEEE). All images are reused with
permission.

Magazine (2), IEEE Microwave and Wireless Components Letters
(1), IEEE Transactions on Microwave Theory and Techniques (1),
IEEE Transactions on Aerospace and Electronic Systems (1), IEEE
Transactions on Instrumentation and Measurement (3) and IEEE
Transactions on Vehicular Technology (2). They are used outside the IEEE in Nature's Microsystems & Nanoengineering (14),
Hindawi's International Journal of Antennas and Propagation
(5) and Springer's Journal of Infrared, Millimeter, and Terahertz
Waves (5). They are found in Austria in E&I (3) and outside,
e.g., they are used in the Electronic Letters (2) of the Institution of Engineering and Technology (IET) and in Science (3)
of the American Association for the Advancement of Science
(AAAS). This list is by no means comprehensive. Typical examples are shown in Fig. 1.
Microsystems & Nanoengineering is of interest, because the
first engineering journal from the Nature Publishing Group
[15] is a relatively young journal with a manageable amount
of publications. As of late 2018, fourteen out of 142 published
articles (9.86%) in the journal used coins as a measure of size.

is a true measurement of the object's size, similar to rulers or
cubes with 1 cm side length.
Arguably, this is not the case when coins cannot be uniquely
identified, e.g., in [16] and [17]. Both use coins that depict Elizabeth II: in [16] "ELIZABETH II D G REG F D 2012" is clearly
readable; in [17] the image quality is poor, but the portrait of
Elizabeth II is recognizable, nonetheless. However, in both
photographs the material of the coin cannot clearly be recognized. Several coins of the pound sterling (GBP) are circularly
shaped and depict the portrait of Elizabeth II on the obverse.
As the exact sizes of the coins are unknown in [16], [17], the
object sizes are not measured. This problem generally arises
when coins cannot be identified due to poor image quality, as
in [18]. From the referenced papers it is not evident whether
coins are used as a measure of length, area or volume. They
qualify as measurement devices for all three, as their whole
geometry is standardized. Therefore, coins are generally classified as a measure of size.

Rule 2. Use of Coins to Measure Size is Not
Explicitly Stated
Measures of an object's size are evident for everyone who
works in the field, and the use of rulers, measurement tape,
drawn dimensions, etc. is therefore not typically mentioned in
the text. However, as for other measurement devices, there are
exceptions where the use of coins is explicitly stated. The most
common place to mention the use of coins is in the caption,
which is done in ten of the investigated works. Use of coins
is explicitly written onto the figure in [9] and [19] as "Coin"
and "Dime for scale," respectively. Another author comments
in the text: "For the first plaster prototypes a thin 800μm FR4
(flame retardant) PCB with the size of a 2 Euro coin was designed (Fig. 3)" [20].

Rule 3. Coins are Not Used as a Measurement
Unit
In the referenced papers coins are never used as a true measurement unit, in the sense that neither multiples nor fractions
of coins are used. A counterexample is shown in Fig. 2, where
the length of a wire is measured as 2.5 EUR fifty cent coins.

Common Practices in Using Coins as
Size Measure
Qualitative analysis reveals a form of unwritten consensus
in the scientific community on how coins should be used as
a measure of size. The rules of using coins as a measure of
size are formulated such that they express the common usage
among the referenced publications. Only counterexamples are
given, meaning that all investigated works that are not explicitly mentioned support the rule. A counterexample is created if
none is available as a reference.

Rule 1. Coins are Used as a Measure of Size
Placing coins next to objects in photos is more than a rough size
reference ("coin-sized"). The geometries of coins are standardized by the issuing authority. Placing a coin next to an object
April 2020	

Fig. 2. The length of a wire is measured as 2.5 EUR fifty cent coins.

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