Practical
Electronics
Editorial offices
Electron Publishing
Tel +61 2 9939 3295
(Australia) Email pe<at>pemag.au
Web www.electronpublishing.com
Address mail to:
Electron Publishing (Australia)
PO Box 194, Matraville NSW 2036
Australia
Advertising enquiries
+61 2 9939 3295
pe<at>pemag.au
Editor
Nicholas Vinen
Publisher
Nicholas Vinen
Digital subscriptions Stewart Kearn Tel 07918 614662
Online Editor
Alan Winstanley
Web Systems
Kris Thain
Production
Bao Smith
Technical staff
Tim Blythman, John Clarke
Print subscriptions
Practical Electronics Subscriptions
PO Box 6337
Bournemouth BH1 9EH
Tel
01202 087631
United Kingdom
Email pesubs<at>selectps.com
Technical enquiries
We regret that technical enquiries cannot be answered over
the telephone. We are unable to offer any advice on the use,
purchase, repair or modification of commercial equipment or the
incorporation or modification of designs published in the magazine.
Questions about articles or projects should be sent to the editor
by email: pe<at>pemag.au
Projects and circuits
All reasonable precautions are taken to ensure that the advice and
data given to readers is reliable. We cannot, however, guarantee
it and we cannot accept legal responsibility for it.
Some projects and circuits published in Practical Electronics
employ voltages that can be lethal. Do not build, test, modify or
fix any mains-powered equipment unless you fully understand
the safety aspects involved and you use an RCD (GFCI) adaptor.
Component supplies
Silicon Chip Publications may offer kits or other parts for making
our projects, but not in all cases. When kits are not available,
readers will need to find and source parts themselves. We advise
readers to check that all parts are still available before commencing
any project in a back-dated issue.
Advertisements
Although the proprietors and staff of Practical Electronics take
reasonable precautions to protect the interests of readers by
ensuring as far as practicable that advertisements are bona fide,
the magazine and its publishers cannot give any undertakings in
respect of statements or claims made by advertisers, whether
these advertisements are printed as part of the magazine, or in
inserts. The Publishers regret that under no circumstances will
the magazine accept liability for non-receipt of goods ordered,
or for late delivery, or for faults in manufacture.
Transmitters/bugs/telephone equipment
We advise readers that certain items of radio transmitting and
telephone equipment which may be advertised in our pages
cannot be legally used in the UK. Readers should check the law
before buying any transmitting or telephone equipment, as a fine,
confiscation of equipment and/or imprisonment can result from
illegal use or ownership. The laws vary from country to country;
readers should check local laws.
2
Volume 54. No. 9
September 2025
ISSN 2632 573X
Editorial
Why I don’t put a space between numbers and units
International standard ISO/IEC 80000 states that “A space should be
used to separate a numerical value and its unit symbol. This space is
a non-breaking space and ideally a thin space in typesetting.”
Reading Practical Electronics, you will have have noticed that we
don’t do that; we put units immediately after a number, for example,
12V, 1.3A or 25°C. This is not because we are lazy; it is a deliberate
convention.
The reason for this is that, when a number has a unit attached, the
numbers and units are inextricably linked. The units can only be
changed by a mathematical transformation between that number/
unit pair and another number/unit pair. To separate the numerical
value any other way is to invite disaster.
So, for example, when calculating 12V × 10, the result is 120V, not
120. However, if you perform the calculation 12V ÷ 10V, the result is
1.2 – a unitless number, not 1.2V. In other words, when operating on
either the number or the unit, you always operate on both.
I don’t think that adding a thin space makes it look any better (you
might disagree). But that is not why we don’t do so; it’s because we
want to reinforce the idea that the two parts are inseparable.
This has real consequences. Too many students (and some
professionals) treat units as afterthoughts, rather than integral
parts of physical quantities. We believe that presenting values and
units as a unified whole helps reinforce the correct mental model:
that “12V” is not just a number with a label, but a distinct and
meaningful quantity that cannot be casually separated.
There’s also a growing awareness in fields like programming, data
science and engineering software that quantities with units are
fundamentally different types to plain numbers. Software libraries
like Pint (Python) or units-aware spreadsheets make this distinction
explicit. If you try to add 12V to 5A, you’ll get an error – and rightly
so. Keeping the unit visually connected to the number supports this
idea of type safety and helps readers avoid conceptual errors.
Finally, it’s worth acknowledging that typographic conventions
were created in the print era, when spacing was as much about
line justification and aesthetics as semantics. Today, we write and
read in digital formats where cut-and-paste, machine parsing, and
semantic clarity often matter more. A thin space may look elegant
in typeset copy, but it makes it far easier for readers to accidentally
copy just the number without the unit.
Nicholas Vinen, Electron Publishing (Australia)*
Publisher & Editor,
Practical Electronics Magazine
* a division of Silicon Chip Publications Pty Ltd.
Practical Electronics | September | 2025
